Your pants ______ dirty. You must wash them at once. [ ]
A. am
B. is
C. are
D. be
答案:C
佝偻病的病因包括()
A.胎中失养
B.先天不足
C.调理不当
D.外感风寒
E.后天亏乏
邮政法第三十八条:任何单位和个人不得有哪些行为出现?