The option that specifies the data directory location at server startup is . . . . . . . .

This question asks about the command-line option you use when starting the MySQL server to tell it where to find the data files.
Think of it like giving your computer directions to your important files. The data directory is where all your database information is stored.
Here's a breakdown of the options:
Option A: -data This is close, but not the exact command used.
Option B: -data_dir This is the correct option! It tells MySQL where to find the data directory.
Option C: -data-dir This is a common way to write options, but it's not the right format for this particular one.
Option D: -datadir While this option is close, it's not the standard way to specify the data directory in MySQL.
So the answer is Option B: -data_dir