根据句意和汉语注释，写出单词的正确形式。

1.  —How many ______(堂兄弟) do you have?    

     —I have three.

2. The students in our school are all ______and helpful (有礼貌的).

3. The boy in a white ______ ( 衬衫) is my cousin Andy.

4. The little children like to play ______ (模型)  planes in the playground.

5. Jiangyin has many  ______ (图书馆). Many people like to borrow books from them.

对于下列应收账款认定，通过实施函证程序，注册会计师认为最可能证实的是（）。

A.计价和分摊

B.分类

C.存在

D.完整性