Can you tell me when _____?[ ]
A. did tea invented
B. tea invented
C. tea was invented
答案:C
沥青复合胎柔性防水卷材中,复合毡胎基比单独聚乙烯膜胎基卷材( )。
A.抗拉强度增高
B.抗压强度增高
C.抗拉强度降低
D.抗压强度降低
霉素钠注射液的皮肤敏感试验药物浓度为()
A.100U/ml
B.250U/ml
C.500U/ml
D.750U/ml
E.1000U/ml