We children of course were only vaguely aware of the extent of our poverty. having no radios few newspapers and no magazines we were somewhat unaware of the world outside our community

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.

the red coloration of the lungs looks alarming and adds to the overall message that the flu is threatening apex