An Amazon RDS MySQL database instance is failing to reboot.Event logs show an error: “MySQL could not be started due to incompatible parameters”. What actions must be performed to resolve this issue?

Answer options:

A.Use SELECT VARIABLE_NAME, SESSION_VALUE, GLOBAL_VALUE statement to identify system variables that have custom values. Use SET statement to set any modified system variables to their default values.
B.Select the default DB Parameter group in the RDS console. Choose the Reset Parameter Group Action to revert the parameters to their default values.
C.Modify the RDS database instance to use the default DB Parameter Group. Reboot the instance.
D.Compare the RDS database instance DB parameter group to the default parameter. Reset any custom parameters to their default values. Reboot the instance.

Answer: D
Option A is incorrect because AWS RDS does not allow modification of MySQL system variables directly using the SET statement. Instead, DB parameter groups must be used.
Option B is incorrect because you cannot modify the default DB parameter group values.
Option C is incorrect because you cannot modify the RDS instance in an incompatible parameters state. You must reset the values of the DP parameter group currently applied to the RDS instance.
Option D is CORRECT because one (or more) parameters are set to non-default values that are not compatible with the current RDS engine or instance class. To resolve the issue, you must reset the parameters to their default values.
Reference:
https://aws.amazon.com/premiumsupport/knowledge-center/rds-incompatible-parameters/