_________ difficult and challenging the task may be, we must finish it on time, because there is a possibility _________we’ll be fired if we can’t fulfill the task on time．

A．Whatever; that

B．However; that

C．Whatever; which

D．However; as

用药物灭鼠的方法属于（）

A.生态学灭鼠法

B.物理学灭鼠法

C.化学灭鼠法

D.生物学灭鼠法

E.医学灭鼠法