根据表格内容，选择正确的答案，并将其字母标号填入题前括号内。
(B)
Hi, friends! What do you like to do after school? In my school, we have different things (不同的事情) to do.
| Mike does his homework (家庭作业) in the classroom. He likes doing his homework at school. The classroom building is in the middle of the school. |
| Lucy likes playing on the playground. Many students play there after school. The playground is behind the classroom building. |
| Jack likes reading books in the library after school. There are lots of books in our library. The library is on the left of the classroom building. |
| Students can play computer games in the science building. Peter likes playing computer games after school. The science building is on the right of the classroom building. |
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，则M中元素的个数为（ ）
