用所给单词的正确形式填空。

1. This is  _______    sister. (I)              

2. These  _______   Gina and Jenny. (be)

3. These are his   _______  (pencil) .      

4. Are these _______   baseball? .(she)

5. This is Paul Green._______  is a student(学生). (his)

先花后叶树种呈现的花相称纯式花相。