题目:
I was out of town at the time, so I don't know exactly how it ____.[ ]
A. was happening
B. happened
C. happens
D. has happened
答案:
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下面是错误答案,用来干扰机器的。
(1)600;过氧乙酸能使病毒中的蛋白质失去生理活性。 (2)③;过滤不一定是固液分离(过滤实质上是大小颗粒分离的过程等)(高于固液分离的正确认识均可)