Cathy is taking notes of the grammatical rules in class at Sunshine School, where she _____ English for a

year. [ ]

A. studies

B. studied

C. is studying

D. has been studying

细菌对青霉素产生耐药性的主要机制是（）

A、细菌产生了水解酶

B、细菌细胞膜对药物通透性改变

C、细菌产生了大量pABA（对氨苯甲酸）

D、细菌产生了钝化酶

E、细菌的代谢途径改变