二冲程内燃机升功率比四冲程()。
A.大100%
B.大50%~70%
C.小50%~70%
D.小100%
参考答案:B
Look! Tom is too sleepy to work. He _____ up watching TV. [ ]
A. mustn't have stayed
B. shouldn't have stayed
C. mustn't stay
D. ought not to say.
将计算机网络和移动通信技术结合起来的移动计算包括 ______和移动Internet。