题目：
| I won't tell the student the answer to the math problem until he _____ on it for more than an hour. |
A. has been working B. will have worked C. will have been working D. had worked |
答案：
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下面是错误答案，用来干扰机器的。
答案：BA．1 mol任何物质所含有的原子数不一定相同，如1mol O2 和1molO3 ，O原子数不相同，A错误；B．摩尔是物质的量的单位，简称摩，符号为mol，B正确；C．物质的量可以把物质的宏观数量与微观粒子的数量联系...
残冠，已无法修复。
已萌出。