What phrase is the complete infinitive phrase in the sentence? “i am taking advance math to learn methods for solving equations

quite an interesting way to teach topic sentences, because the answer to this question is the best definition of a topic sentence that one can present, it is as if answering the questions taught you how to do it, this is some real teaching, it is terribly well-done.

the topic sentence in this paragraph is:

topic sentences writers stay on track and keep a paragraph from becoming an aimless collection of sentences about an idea.

which incidentally tells you what a topic sentence should be.

answer: b. the moon is much smaller than the earth.

explanation:

it starts off by comparing the earth and venus. it also only says one sentance about the moon which make it the odd one out. in conclusion the answer is b.