Astudent with adhd who has trouble waiting his turn, resisting distractions, delaying immediate gratification, or interrupting a faulty line of thinking is having problems with:

I believe the answer is: behavior inhibition

behavior inhibition refers to the tendency that people have to withdraw ourself from the situation that seem 'unfamiliar' for us.
In the scenario above, that student cannot delay his/her gratification because that student is not familiar with the reward that might come because of the delayed gratification.

B. it promoted the powers of the executive branch