Explanation:

Attribute Groups are the organizational structure within Contact Builder's Data Designer. Their purpose is to define how data extensions relate to each other and, most importantly, to the central Contact record.

B. They link data extensions to contacts: The primary function is to link the Root Data Extension of the group (often the Customer or Subscriber DE) to the central Contact Data model using the Contact Key. This allows Journey Builder and other apps to access the data.

C. They link data extensions to other data extensions: Within the group, you define the relationships (One-to-One, One-to-Many) between the various data extensions (e.g., linking the Orders DE to the Customer DE).

❌ Incorrect Answers:

A. They link data extensions to subscriber lists: Lists are a legacy, non-relational data model. Attribute Groups are used for the Data Extension (relational) model.
D. They link subscriber lists to contacts: The link is always between Data Extensions and the central Contact record.

📄 Reference:
Salesforce Trailhead - Contact Builder Data Designer: "The Attribute Groups area of Data Designer links data extensions in Contact Builder to your contact record." "Attribute Groups are groups of attributes and the data extensions where they live. Attribute Groups link data extensions to the Contact Key and define the relationships among your data extensions."

Explanation:

B. AMPscript can be used to pull data from Send Logs for use within emails.
This is correct and one of the most powerful features of Send Logging.
After Send Logging is enabled, every send automatically writes a row to your Send Log Data Extension containing whatever additional fields you defined (e.g., Order_ID, Coupon_Code, Preferred_Store, Device_Type, etc.).
At send time in any future email (triggered, journey, or regular send), you can execute real-time AMPscript functions such as Lookup(), LookupRows(), or LookupOrderedRows() against that Send Log DE using SubscriberKey, SubscriberID, or JobID as the key.
Real-world examples used by many enterprise clients:
- Show the exact product a subscriber last clicked
- Display the last coupon they redeemed so you don’t offer it again
- Remind them of an abandoned cart item with dynamic images
- Suppress content they already acted on
This personalization capability is a core reason large senders invest in Send Logging.

D. SQL Query Activities can reference Send Logs in combination with system data views.
Absolutely correct and heavily used in advanced implementations.
The Send Log is simply a standard Data Extension, so it can be freely joined in Automation Studio SQL Query Activities with any system data view (_Sent, _Open, _Click, _Bounce, _Unsubscribe, _Journey, _JourneyActivity, etc.).
Common use cases:
- Build a report of everyone who received a specific dynamic coupon and later clicked the redemption link
- Create suppression lists for offers already redeemed
- Calculate true attribution when multiple emails contributed to a conversion
- Feed Einstein or external analytics platforms with enriched behavioral data
You typically join on SubscriberKey + JobID + BatchID or custom keys you logged.

Why A is incorrect
Send Log Data Extensions are NOT automatically archived. Retention is 100% manual. You define the data retention policy on the Send Log DE itself (e.g., keep 90 days, 180 days, or indefinite). Salesforce never auto-archives or purges Send Log rows unless you explicitly configure it.

Why C is incorrect
There is no limit of “three Send Logs” per business unit. You can create as many Send Log templates and corresponding Data Extensions as you need (most organizations use just one, but there is no technical restriction to three).

References
Send Logging Overview
Using AMPscript with Send Logging  (official examples)
Data Views and Query Activities

Explanation:

C. Create a Journey with a Salesforce Campaign entry source and an Email Activity
Explanation: This is the best practice for sending emails to an audience that is already organized within Salesforce CRM as a Campaign.

Salesforce Campaign Entry Source: This entry source allows you to select a specific Salesforce Campaign. It automatically listens for contacts or leads who are added to that campaign in Sales Cloud and injects them into the Marketing Cloud Journey.

Automation and Timing: The journey can be configured to run as a single batch (for a one-time blast) or on a recurring schedule (to catch new campaign members), eliminating the need for complex, separate automation activities.

Email Activity: Once contacts are in the journey, the Email Activity (or a series of activities) deploys the message, ensuring a streamlined and targeted send based directly on the CRM's segmentation.

❌ Less Suitable Answers and Explanations

A. Create a scheduled Automation with a Query Activity and a Send Email Activity
Why it's less suitable: This is used to segment data that already lives in Marketing Cloud Data Extensions. To target a Salesforce Campaign, you would first need to Synchronize the Campaign Member object via Marketing Cloud Connect, then write a complex SQL Query to extract those members into a Sendable Data Extension. This is more work and less efficient than the out-of-the-box Journey Builder entry source.

B. Use Content Builder Send Flow to send the email to the Salesforce Campaign
Why it's less suitable: The Content Builder Send Flow is a manual, one-time deployment process. It is used for immediate, ad-hoc sends, but it does not satisfy the likely need for an automated or recurring process, which is often the reason for setting up an email program.

D. Create a Journey with a Salesforce Data entry source and an Email Activity
Why it's less suitable: This entry source is best for triggering an email based on a change in a CRM record (e.g., a field value changes, or a new record is created). It is an event-based trigger, not the most direct method for sending to a static or periodically updated group of people defined by a Salesforce Campaign. The Campaign Entry Source (Option C) is specifically designed for this purpose.

Explanation:

✔ C — Create a Journey with a Salesforce Campaign entry source and an Email Activity
Journey Builder allows real-time entry of contacts when they are added to a Salesforce Campaign. This ensures immediate delivery of a welcome email when a contact joins the “Loyalty Member” campaign.

❌ A — Scheduled Automation
Automation Studio is suitable for batch processing, not real-time campaign-triggered sends.

❌ B — Content Builder Send Flow
Send Flow is manual and not triggered by Salesforce Campaign events.

❌ D — Journey with Salesforce Data entry source
Salesforce Data entry source is for objects like Contacts or Leads; Campaign entry source is specifically needed for triggering off campaign membership.

Best practices:
Use campaign entry events for loyalty or marketing programs.
Combine with decision splits for personalized welcome content.

References:
Journey Builder Salesforce Campaign Entry Source Guide

Explanation:

Explanation of each option:
A. Using Mobile Studio, create a Mobile Push Filtered List filter on the MobilePush Demographics attribute group.
Correct.
This is the fastest, easiest, and officially recommended way to target everyone who has opted in to push notifications. In Mobile Studio → MobilePush → Overview → Filtered Lists, you can create a filter on the MobilePush Demographics attribute group where Opted In = True (or simply “Device ID is not null”). The resulting list updates automatically and can be used directly in message sends.

B. Using Automation Studio, query the _MobilePushDemographics Data View and save this to a data extension.
Incorrect.
While technically possible, this is not one of the two best/recommended methods. It requires writing and maintaining a query, scheduling an automation, and does not automatically reflect real-time opt-in/opt-out changes as cleanly as the filtered methods do.

C. Using Journey Builder, target the entire customer database then filter using MobilePush Demographics attribute group.
Incorrect.
Journey Builder does not let you apply MobilePush Demographics filters at entry unless you use a pre-built filtered Data Extension or Filtered List. Starting from “All Contacts” and trying to filter inside the journey on MobilePush attributes is not supported for push messages.

D. Using Contact Builder, create a Filtered Data Extension from All Contacts where there is a record in MobilePush Demographics.
Correct.
This is the second officially supported and widely used method. In Contact Builder → Data Designer → Create → Filter → Filter on Attribute Group “MobilePush Demographics” → Device ID is not null (or Opted In = True). The resulting Filtered DE stays up-to-date automatically and can be used as an audience for MobilePush messages or Journey Builder entry sources.

Recommendations
Salesforce documentation and Trailhead explicitly list Filtered Mobile Lists in Mobile Studio and Filtered Data Extensions in Contact Builder based on MobilePush Demographics as the two primary ways to target opted-in push subscribers.