Answer:
A. a call to action
Step-by-step explanation:
Obviously, when ending an essay an opening will not be used, so option D can be ruled out immediately.
While a topic and thesis restatement should be included in your conclusion paragraph, they normally become before your final sentences of the essay. Also, they introduce nothing new or exciting to the essay and therefore are unable to help with "ending with impact".
A call to action is a common way to get your audience to think about what should be done in the world as a result of what you wrote your essay about. It invokes deep thought in them, and might even inspire them to act in your favor.
Hope this helps!