A view can refer to multiple tables via . . . . . . . .

Answer: Option B

This question is asking about how views in MySQL can access data from multiple tables.

Let's break it down:

* Views are like virtual tables that don't actually store data. They just present a specific way to look at data from real tables.
* UNION combines results from different queries, but it's not the way a view references multiple tables.
* JOIN is the key here! A JOIN combines data from two or more tables based on a shared column. Views can use JOIN to bring data from multiple tables into a single view.
* GROUP is used for summarizing data within a table, not for combining tables.
* SELECT is a basic operation for retrieving data, but not for creating a view that references multiple tables.

Therefore, the correct answer is Option B: JOIN.