Which type of configuration variables CANNOT be modified in MySQL custom configurations?

Initialization variables(Answer A) cannot be modified in MySQL custom configurations. These variables are set at the start of the MySQL service and are not changeable without restarting the service.

Initialization variables are parameters that define how the MySQL server initializes.

Changes to these variables require restarting the MySQL server to take effect.

Examples include variables likeinnodb_buffer_pool_size, which determine memory allocation settings on startup.

References:

MySQL Configuration Variables Documentation