The statement that is used to check the status of the event scheduler at runtime is . . . . . . . .

This question is about checking the status of the event scheduler in MySQL. The event scheduler is a feature that allows you to schedule tasks to run automatically at specific times or intervals.

To find out if the event scheduler is currently running, you use a special command called SHOW STATUS or SHOW VARIABLES. These commands provide information about various aspects of the MySQL server.

Here's how the options work:
* Option A: SHOW STATUS OF 'event_scheduler' - This option is incorrect because the syntax for using `SHOW STATUS` is different. You don't use `OF`, you use `LIKE`.
* Option B: SHOW VARIABLES OF 'event_scheduler' - This option is incorrect for the same reason as Option A. You need to use `LIKE` instead of `OF`.
* Option C: SHOW STATUS LIKE 'event_scheduler' - This option is correct. The `SHOW STATUS LIKE 'event_scheduler'` command will show you the current status of the event scheduler, whether it's ON (running) or OFF (stopped).
* Option D: SHOW VARIABLES LIKE 'event_scheduler' - This option is also correct. The `SHOW VARIABLES LIKE 'event_scheduler'` command will show you the current status of the event scheduler, whether it's ON (running) or OFF (stopped).
So, the answer to the question is either Option C or Option D. Both options will give you the same information about the event scheduler's status.