What jobs "Query Optimizer" perform in Mysql?

Answer: Option A

Determine the efficient way to execute a query: The primary task of the Query Optimizer is to analyze SQL queries and determine the most efficient execution plan. It evaluates various factors such as available indexes, table statistics, and the structure of the query to generate an optimal execution plan that minimizes resource usage and maximizes performance.
Syntax errors: Syntax errors are typically detected by the MySQL parser during query compilation and are not directly related to the Query Optimizer's function.
Permissions: Permissions management, such as granting or revoking privileges, is handled by the MySQL privilege system and is not directly related to the Query Optimizer's function.
All of the mentioned: While the Query Optimizer is responsible for determining the efficient way to execute a query, it is not involved in handling syntax errors or managing permissions. Therefore, the correct option is not All of the mentioned.

Therefore, the task performed by the Query Optimizer in MySQL is Option A: Determine the efficient way to execute a query.