Explanation:

In Salesforce Marketing Cloud Social Studio, the Engage Tab is a workspace that allows users to monitor, view, and interact with social conversations across multiple accounts and channels in real-time. Think of it as your centralized social listening and engagement hub.

When setting up an Engage Tab, you can create multiple columns to monitor different content streams, like:

Specific social media accounts (Facebook, Twitter, LinkedIn, Instagram, etc.)
Keyword searches
Hashtag mentions
Direct messages
Brand mentions
Custom queries

Each column represents a specific content feed based on filters or account selections.

📊 Key Facts About Engage Tabs and Columns:

Engage Tabs:
You can create a maximum of 30 Engage Tabs per user (or per workspace, depending on the configuration).
Each Engage Tab is like a dashboard, containing various columns.

Columns in Each Engage Tab:
There is no technical limit to the number of columns you can create in each Engage Tab. This means that users can create as many columns as necessary, depending on their monitoring needs.
Practically, however, Salesforce recommends keeping the number of columns manageable for usability reasons (e.g., screen space, load performance).

Accounts per Column:
Each column can monitor up to 50 social media accounts simultaneously.

❌ Why Other Options Are Incorrect:

A. 50
Incorrect. 50 is the limit on the number of accounts per column, not the number of columns themselves.

B. 100
Incorrect. There’s no 100-column limit. The system allows unlimited columns within each Engage Tab.

C. 15
Incorrect. This number doesn’t relate to any known limit regarding columns or tabs.

📖 Reference:
Salesforce Social Studio Documentation – Engage
Salesforce Social Studio Admin Guide