阅读下面短文，掌握其大意，然后从每题所给的A、B、C、D四个选项中选出一个最佳选项。

    My name is Jenny. I am twelve years old. I have some   1 . They are Mike, Jack, Mary and Kate. We are middle school   2  . Mike and Jack   3  in the same class.  4are in Class Two, Grade One. Mary, Kate and I are  5  Class Three. This is Mr. Green.  6is our English teacher. This is 7new classroom. In the classroom, you can see 45 desks and chairs. They are green. A blackboard, a clock and a map are  8 the wall. On a desk you can see  9  pencils. The red one is mine. The green one is Kate's. The yellow one is Mary's. Mike's pencil isn't there. His pencil is in his bag.

    Look! You can see a ball under a desk. That's Kate's desk. The ball is   10 , too. This is my desk. You can see some books on it. They are our new books.

①形成四分体   ②同源染色体分离   ③交叉互换   ④联会   ⑤染色体复制   ⑥染色单体分离．