Introduction:
SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases. It consists of various categories of commands that perform different functions. This response will explain the categories of SQL commands and clarify why option 'B' is not a valid category.

Categories of SQL Commands:
1. DDL (Data Definition Language):
- DDL commands are used to define and manage the structure of a database.
- They include commands such as CREATE, ALTER, DROP, and TRUNCATE.
- These commands are responsible for creating, modifying, and deleting database objects like tables, views, indexes, and constraints.

2. DML (Data Manipulation Language):
- DML commands are used to manipulate or retrieve data within the database.
- They include commands such as SELECT, INSERT, UPDATE, and DELETE.
- These commands allow users to insert, update, delete, and retrieve data from tables.

3. DQL (Data Query Language):
- DQL commands are used to retrieve data from the database.
- The primary command in this category is SELECT, which is used to extract data based on specific conditions.
- DQL commands are essential for retrieving information from the database and are often used in conjunction with DML commands to perform complex data operations.

4. DCL (Data Control Language):
- DCL commands are used to control the access and permissions of database users.
- They include commands such as GRANT and REVOKE.
- DCL commands are used to grant or revoke privileges and permissions, controlling who can access or modify the database.

Explanation of the Correct Answer:
The correct answer is option 'B' because there is no specific SQL command category called "DML (Data Population Language)." The term "Data Population Language" is not recognized as a standard category in SQL.
- SQL commands related to data manipulation are included in the DML category.
- DML commands like INSERT, UPDATE, and DELETE are responsible for manipulating data within the database.

Conclusion:
To summarize, the categories of SQL commands include DDL (Data Definition Language), DML (Data Manipulation Language), DQL (Data Query Language), and DCL (Data Control Language). The option 'B' is not a valid category as there is no specific category called "DML (Data Population Language)" in SQL.