The following are all traffic signs except ____. [ ]
答案：C
— Who ____________ Ben and Tim?
— They ____________ my classmates.[ ]
A. is; is
B. is; are
C. are; are
D. are; is
社会保障实质是()。
A．经济保障
B．政治保障
C．思想保障
D．社会保障
