The library file that contains various portability macros and definitions is . . . . . . . .

Solution (By Examveda Team)

This question is about a special file in MySQL that helps it work on different types of computers. This file has helpful instructions and settings that tell MySQL how to adjust itself to work correctly on various systems.

Think of it like a set of instructions for a toy that can be played with on different surfaces, like sand, grass, or carpet. These instructions tell the toy how to behave on each surface so it works properly.

In MySQL, the file that contains these instructions is called a "header file". These files are important because they allow MySQL to function correctly on different operating systems like Windows, macOS, and Linux.

Now, let's look at the options:

Option A: my_global.h - This file holds global settings for MySQL, but it doesn't specifically focus on portability.
Option B: my_sys.h - This is the correct answer! This file holds system-specific definitions and macros that help MySQL adapt to different environments.
Option C: mysql.h - This file contains the main definitions for working with MySQL.
Option D: my_local.h - This file contains local settings for MySQL, not portability-related instructions.

Therefore, the correct answer is Option B: my_sys.h. This file is crucial for making MySQL work seamlessly on different computers.