建筑变形缝有（）三种。
A.预留缝
B.伸缩缝
C.沉降缝
D.防震缝
E.垂直缝
参考答案：B, C, D
Do you know（）at the bus stop?
A.whom they are waiting for
B.who they are waiting
C.whom are they waiting for
D.who are they waiting
80C51复位后，PC与SP的值为（）。
A.0000H，00H
B.0000H，07H
C.0003H，07H
D.0800H，00H
