The correct answer is D. Supporting evidence
Explanation:
In writing, the main idea is the main point the author writes about which is usually connected to an argument, position, point of view, etc. This main or central idea is the one that guides all the process of writing and that is introduced in the first paragraph, then developed in the body paragraph and restated or summarized in the last paragraphs. Additionally, main ideas are commonly developed through supporting evidence that includes sub-ideas, reasons, quotes, example, statistics, etc organized in multiple paragraphs. Thus, a writer needs to develop the main idea by using supporting evidence.
D. In an encyclopedia under the word “dictionary”
