下列过程中，没有发生化学变化的是[ ]
A．醋除水垢
B．粮食酿酒
C．金块抽丝
D．铜器锈蚀
答案：C
It was ________ he came back from Africa that year ________ he met the girl he would like to marry.[ ]
A. when; then
B. not; until
C. not until; that
D. only; when
在鸡胚和培养细胞中生长一般不引起明显病变的是
A．流感病毒B．麻疹病毒C．副流感病毒D．风疹病毒E．呼吸道合胞病毒
