Upton sinclair wrote the jungle in order to expose a. scandals in washington politics. b. the gruesome conditions in prisons. c. fraud in local and federal governments. d. shocking conditions in chicago stock yards.

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.

1, 4, and 5 are all conflicts