Answer:
The best answer to the question: To determine the central idea of "An Essay on Man", what should the reader do first, would be, D: Identify the topic.
Explanation:
"An Essay on Man" is a poem that was written by Alexander Pope, and which was published in 1733-34. Essentially this poem´s main purpose is to try and justify the workins of God towards Man, but most importantly to try to portray God´s workings as truths that have to be accepted my man as absolutes that cannot be understood, but just accepted as they are.
When we are trying to find central ideas on either a text, or a simple paragraph, the first thing we must always locate first is the topic sentence, and after finding it, we must look for the key details that back the topic sentence. Topic sentences are basically the main ideas inside texts and by finding them we can basically map out the ideas set forth by a writer.