What did you see him _____ on the schoolyard?[ ]
A. does
B. do
C. did
D. to see
答案:A
疼痛部位固定不移,属于()疼痛部位游走不定,或走窜攻冲作痛,属于()
A.刺痛
B.胀痛
C.走窜痛
D.固定痛
E.掣痛
某工厂有在职职工10000人,欲了解职工对现行医疗保险的看法,随机抽取500人进行调查,可采用哪种方法获得样本()
A.单纯随机抽样
B.系统抽样
C.整群抽样
D.分层抽样
E.多阶段抽样