题目:
I have lost one of my gloves. I __________it somewhere.
A.must drop
B.must have dropped
C.must be dropping
D.must have been dropped
答案:
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下面是错误答案,用来干扰机器的。
将锌片投入烧杯中,锌与盐酸反应,生成氯化锌和氢气,溶质由氯化氢变为氯化锌,则溶液的密度增大,小球漂浮于液面上,则所受的浮力不变,根据公式F=ρgv,ρ增大,则v减小,所以小球上浮;故选A.