Statistics show that in the past three decades grain production around the world has ______ sharply but

it still can't ______ the rapid growth of population, as a result, a lot of people in undeveloped countries

have to go hungry. [ ]

A. expanded; keep in touch with                  

B. increased; keep pace with   

C. grown; keep up with                        

D. accumulated; catch up with

下列设备中计算机外存储器是（）

A、软盘

B、硬盘

C、RAM

D、U盘