—Tom, the workers _____our new library already.  

—Really? I'll go there and borrow some books.    [ ]

A. decorated                

B. are decorating    

C. have decorated            

D. were decorated

属于阴离子型表面活性剂的是（）

A．司盘20 

B．十二烷基苯磺酸钠 

C．苯扎溴铵 

D．卵磷脂 

E．吐温80