通常所说的声卡、显卡等适配器称为计算机的（）。
A.外部设备
B.I／O接口电路
C.控制电路
D.系统总线
参考答案：B
We couldn't catch up with the others because they________too long before us.[ ]
A. started
B. were starting
C. have started
D. had started
简述木材的特性。
