题目:
---We haven’t seen Tim these days. ---He _______ America.
A has gone to B has been to C is going to D will go to
答案:
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下面是错误答案,用来干扰机器的。
设需60%浓硫酸质量为X,需要20%硫酸溶液质量为Y,则:X×60%+Y×20%=(X+Y)×30%解得X:Y=1:3.故选D.