铲运机制动系统同时要求（）。
A．手制动、脚制动，排气制动
B．手制动、脚制动
C．排气制动、脚制动
参考答案：A
The scientists claimed( 声称) to _______ a jet plane that uses atomic energy as propelling _____,
but they can’t produce an atom of evidence to prove it. [ ]
A. design; power
B. have designed; power
C. design; force
D. have designed; strength
近代地球科学证实，石油、天然气和煤，都形成并大多聚集于（）中。
A.岩浆岩
B.沉积岩
C.石灰岩
D.变质岩
