Answer:
The topic, medium, and supporting sentences
Step-by-step explanation:
The central idea of a paragraph is its most important, relevant or main thought. Three key elements that will help us identify it are the topic because it can indicate us the matter dealt with in the paragraph, the medium (the form or material used by an author to express their ideas) because, for example, the ideas expressed in an essay's paragraph, which is an academic writing, can be widely different from those expressed in a blog, which tends to be more personal and informal, and the supporting sentences since they give us more details that will help to infer the main thought.