You need to create a timer job that queries a list.

What should you do?

A.
Create a class that inherits SPJobDefinition and override the Execute method.

B.
Create a class that inherits SPJobDefinition and override the Provision method.

C.
Create a class that inherits SPServiceApplication and override the Provision method.

D.
Create a class that inherits SPServiceApplication and override the ProvisionInstances method.

Explanation:
MNEMONIC RULE: “Execute timer job”

Next, and the most important thing, is to override Execute() method. This method is called each time when the job is fired, so it should contain all the logic to accomplish what You expect from the job.

SPJobDefinition as the way to create scheduled tasks
http://tomaszrabinski.pl/wordpress/2010/05/27/spjobdefinition-as-the-way-to-create-scheduled-tasks/