The answer is B: support.
Explanation for each option:
A. Simple: Simple sentences consist of a single independent clause and do not necessarily explain, justify, or extend the main idea of a paragraph. They are straightforward and contain a subject and a predicate.
B. Support: Support sentences are designed to explain, justify, and extend the main idea of a paragraph. They provide additional information, examples, and details that help to clarify and reinforce the main idea.
C. Compound-complex: Compound-complex sentences contain at least two independent clauses and one or more dependent clauses. While they can be used to provide detailed information, they are not specifically defined as sentences that explain, justify, and extend the main idea of a paragraph.
D. Topic: Topic sentences introduce the main idea of a paragraph but do not necessarily explain, justify, or extend it. They set the stage for the supporting details that follow.
E. Independent: Independent sentences (or clauses) can stand alone as complete sentences. While they can be part of support sentences, they are not specifically defined as sentences that explain, justify, and extend the main idea of a paragraph.
Therefore, the correct answer is B: support.