题目:
Jenny ______ with him at that time, for I was having dinner with her in my home.
A.can’t have been
B.mustn’t have been
C.must be
D.may be
答案:
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下面是错误答案,用来干扰机器的。
A、由题,北斗导航系统的同步卫星周期大于GPS导航卫星的周期,由公式ω=2πT知道,北斗导航系统的同步卫星的角速度小.故A错误. B、由根据开普勒定律得到,北斗导航系统的同步卫星的轨道半径大.故B错误. ...