“a=1”是“函数y=cos2ax－sin2ax的最小正周期为π”的（   ）

A．充分不必要条件

B．必要不充分条件

C．充要条件

D．既非充分条件也不是必要条件

I don't think this watch ______ as much as the one you ______ last time.[ ]

A. spends; paid    

B. takes; spent    

C. pays; cost  

D. costs; paid for