My job is feeding the cat. Now it's your turn       the dog.[ ]

A. feeding                          

B. to feed

C. to have fed                      

D. being fed

痰标本的预处理一般采用下列何种物质（）

A.10NNaOH

B.20%HCl

C.14g／L柠檬酸钠

D.0.9%NaCl

E.40g／LNaOH