以下作用于细菌细胞壁的药物是（）
A.阿奇霉素
B.阿米卡星
C.利奈唑烷
D.哌拉西林
E.氧氟沙星
参考答案：D
Not until all the fish died in the river _____ how serious the problem of water pollution was. [ ]
A. did they realize
B. they did realize
C. had they realized
D. they had realized
钢板在冷却后须经什么工序才能成材？为什么？
