Central idea is also known as main idea. Definition: The central idea (main idea) in a piece of writing is the point that the author wants you to remember most. Some writers may state the main idea, but it is often implied, which means the reader has to make inferences (what the text says + what I know) about it.
The affix for without would be non-
Expository writing is used to convey factual information (as opposed to creative writing, such as fiction). It is the language of learning and understanding the world around us. If you've ever read an encyclopedia entry, a how-to article on a website, or a chapter in a textbook, then you've encountered examples of expository writing
So a or d but i'm leaning toward d
