— Is he from America?
— _____. [ ]
A. Yes, he does
B. No, he doesn't
C. Yes, he is
答案:C
违约频率是事后检验的结果。()
青霉素中引起过敏的杂质主要是()
A.青霉噻唑酸
B.青霉噻唑多肽
C.水解产物
D.青霉胺
E.青霉菌