The subject-verb agreement rule which is being broken in the sentence above is c<span>ollective subjects functioning as a unit require singular verbs.
The collective subject <em>the crew </em>requires a singular verb, because it denotes a single unit. So, instead of using the verb <em>have visited, </em>it should have been <em>has visited. </em></span>
The topic sentence is, of course, a sentence where you state the main topic of your paper. You want people to know your topic as soon as possible. Therefore, answers A and D are obviously places you would most commonly put your topic sentence. However, you can also put it in your body of your paper. But the one place you never want to put your topic sentence is answer C, in your conclusion paragraph.
Most likely it will be found under textbook :)