Some equipment as well as a number of maps and books ________ to the area since the earthquake

occurred. [ ]

A. has been offered  

B. have been offered

C. is being offered  

D. are offered

氮芥类是（）。

A．β-氯丙胺类的总称

B．β-氯乙胺类的总称

C．β-氯丁胺类的总称

D．α-氯丙胺类的总称

E．α-氯乙胺类的总称