Explanation:

To ensure that a picklist field always has a value when a record is created or updated, the most efficient and enforceable approach is to:

✅ C. Mark the field as Required on the field definition

Setting a field as required at the field level (schema definition) ensures that no record can be saved (via API, Apex, UI, Flow, etc.) unless the field has a value.
This enforcement is universal — meaning it applies across all entry points.
This is the most efficient and robust method.

🔹 Reference: Salesforce Help: Make a Custom Field Required

❌ Why the others are incorrect or less ideal:

A. Set "Use the first value in the list as the default value" as True

This only sets a default value, but users or processes can still clear or override it.
It does not enforce that a value must be selected during record creation or update.

B. Set a validation rule to enforce a value is selected

This can work, but is less efficient than using the built-in "required" flag.
Also, it's additional configuration and logic that is unnecessary when a simpler declarative option (field-level required) exists.

D. Mark the field as Required on the object's page layout

This only makes the field required in the UI and only on that specific layout.
It does not enforce the requirement via API, Apex, Flow, or even other layouts.

Explanation:

Record-triggered flows are the most efficient and declarative way to automate logic when a record is created or updated. In this case, you want to create a Task when an Opportunity is created—this is a perfect use case for a record-triggered flow on the Opportunity object.

The flow will fire when a new Opportunity is inserted.
It can automatically create a Task with the appropriate fields.
It can assign the Task to the Opportunity Owner using simple field references.

This solution is low-code, easy to maintain, and recommended by Salesforce over Apex for straightforward logic.

❌ Why Not the Other Options?

A. Auto-launched flow on Task
🔴 Not suitable, as this type of flow does not automatically trigger on record creation. You would need another mechanism to call it.

B. Apex trigger on Task
🔴 Incorrect object. The logic needs to fire on Opportunity creation, not when a Task is created. Also, Apex is not necessary for this simple requirement.

C. Task actions
🔴 Task actions are typically used for UI-based interactions, such as Quick Actions on a record. They do not automatically create Tasks upon Opportunity creation.

Explanation:

C. At least 75% of Apex code must be covered by unit tests

Salesforce requires that at least 75% of Apex code is covered by unit tests before you can deploy to production. This is a mandatory requirement to maintain code quality and reliability in the production environment.

B. All triggers must have at least one line of test coverage

Every trigger must be tested, even if it's just one line of coverage. If any trigger has 0% coverage, Salesforce will block the deployment. This ensures that triggers won’t cause runtime issues in production.

Explanation:

- A Formula field is the most efficient way to calculate the ratio between rejected and approved timesheets dynamically.
- Since the Rollup Summary fields already aggregate the total approved and rejected timesheets, a formula can simply divide these values to compute the ratio.
- Formula fields require no maintenance, unlike triggers or flows, and they update automatically whenever the underlying data changes.

Key Takeaways:

✅ Formula field (B) is the simplest, most sustainable solution.
🚫 Avoid unnecessary automation (A/C/D) for static calculations.

❌ Why other options are not ideal:

A. Record-triggered flow

❌ Overkill for a basic calculation that doesn’t require automation logic.
More complex and requires maintenance.

C. Apex trigger

❌ Not needed — adds unnecessary code and testing overhead.
D. Field Update actions

❌ Limited to specific scenarios, and not real-time unless tied to automation (like workflow or process builder).

Explanation:

Since the requirement is to create a new Contact record and then store its ID in the Opportunity, the best approach is to use the Create Records element within the flow.

Steps to Update the Flow:
Add a "Create Records" element → This will generate a new Contact record based on the necessary field inputs.
Store the newly created Contact's ID in a variable or directly in the Opportunity.
Modify the "Update Records" element to include the stored Contact ID and associate it with the Opportunity record.

Why Not A, C, or D?

A. Add a Get Records element → This retrieves existing records but does not create a new Contact, which is required.
C. Add an Update Records element → While updating the Opportunity is necessary, it cannot create a Contact—a "Create Records" action must come first.
D. Add a Roll Back Records element → Used for undoing changes if errors occur, but does not contribute to creating or storing new records.