Final answer:
A good paragraph should include a topic sentence and a specific purpose. Coherence is crucial, and the number of sentences can vary as long as the idea is fully developed.
Step-by-step explanation:
A good paragraph should have several key components to ensure it communicates its message effectively. First and foremost, a good paragraph contains a topic sentence that clearly indicates the main idea or point of the paragraph. Following the topic sentence, the paragraph should present a reason for the topic sentence's claim, an illustration of the topic sentence's point, an explanation of the sentence's point, or evidence demonstrating the topic sentence's point. It's essential to maintain coherence within the paragraph, meaning that all the sentences should be logically connected and follow in a way that makes sense. Additionally, a good paragraph is designed with a specific purpose in mind, whether that's to argue, inform, describe, or explain something related to the topic at hand. A paragraph typically does not require a fixed number of sentences; however, it should be long enough to fully develop the idea, but concise enough to keep the reader's interest.
Therefore, the components that a good paragraph should have are: B. A topic sentence and D. A specific purpose. Options A and C are not characteristic of a good paragraph as the number of sentences can vary and incoherence would detract from the quality and understandability of the writing.