When you list specific details about the main ideas of your subject in order to choose one list to develop, you are narrowing your topic listing sources generating your topic gathering details

The answer is indeed letter A) narrowing your topic.

Explanation:

From the questions, we learn that the person already has a subject/topic. The person has also made a list concerning the main ideas connected to such topic. However, not all of those ideas can or should be developed in their essay. The person, then, lists the specific details of each idea with the intention of choosing one list to develop. That means that person is narrowing their topic, choosing what is worth discussing and developing in order to convey their desired message.

For instance, my topic could be the influence of African slaves in Brazilian culture. Since this topic can be extended to several subtopics, such as food, clothes, religion, music, literature and so on, I should make a list of all the details and decide which ones I wish to discuss further. That will prevent my essay from losing focus and being too long and complex. That is "narrowing your topic".

the correct answer would be:  

a. adverb phrase

a i thinkmark me brainliest