根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    Hello! I'm Jane from Canada. I like my school a lot. It's not big 1 it's very nice. All my teachers and classmates are 2 to me. I love3 very much. We study English, math, art and some other 4. Some subjects are  5, but some of them are boring. Of all of them, I like 6 best, because I like drawing pictures. Oh, my favorite 7 are Tuesday and Friday. On these     8 days, we have art lessons. I don't like politics 9 it's boring and difficult.

    My friend Susan 10 at my school. I often go to school with her. She likes politics. She thinks it's easy.

人和艾滋病病毒的遗传物质的基本组成单位分别有几种(        )

nose