Helen is _____ to her mother. [ ]
A. writing
B. writing
C. writes
答案：B
35. —Tom took away our teacher’s cell phone without being permitted.
—Really? I can’t imagine that he _______ have done such a thing.
A．must
B．may
C．should
D．Can
试简述时钟信号缺失对基站系统运行的影响？
