按要求完成句子，每空一词。

1．These are pencils．(改为单数句)

      ________ ________ ________ ________．

2．He plays sports every day．(改为一般疑问句)

     ________ ________ ________ sports every day?

3．The card is in the drawer．The book is in the drawer．(合并为一个句子)

      The card ________ the book ________ in the drawer．

4．Are they your father and mother? (改为同义句)

      Are they your ________?

5．She has a white tennis racket．(对划线部分提问)

       ________ ________ she ________?

在根的次生构造中有一些径向排列的薄壁细胞群，称（），包括（）和（），其功能是（）。