What is the characteristic of a good topic sentence?
a. it makes inferences about the main idea.
b. it conveys the subject of the paragraph.
c. it refers to the author’s purpose for writing.
d. it supports the main idea of the paragraph with evidence.

The correct answer is B. It conveys the subject of the paragraph.

Explanation:

A paragraph is usually composed by a topic sentence and a set of supporting details, in the case of the topic sentence, this is a phrase or sentence that is usually the first sentence in  the paragraph and that expresses what the paragraph is about, this means in the topic sentence the main idea of the paragraph is set. In the case, of the supporting details, these are the other sentences of the paragraph that explain the main idea or the idea expressed in the topic sentence. Thus, a good topic sentence is a sentence that expresses or conveys the subject of the paragraph or what the paragraph is about.

mark twain, real name samuel langhorne clemens, was an american writer, humorist, entrepreneur, publisher, and lecturer. among his novels are the adventures of tom sawyer and its sequel, the adventures of huckleberry finn, the latter often called "the great american novel". wikipedia