20. which general staff member directs all responses and tactical actions to achieve the incident objectives?

The general staff member who directs all responses and tactical actions to achieve the incident objectives is:

The operation Section Chief

Explanation:

The operation section chief is responsible for managing all operations and progress related to the incidents.The operation section chief is responsible for developing the strategy as well as for the implementation of this strategy and tactics to carry out the objectives established by the Incident Commander.The operation section chief holds a primary place in the Incident command system who is responsible for the accomplishment of the primary goal.

It's most likely choice a, it makes the most sense in my opinion.