题目：
| — How long _____ at this job? — Since 1990. |
| A. were you employed B. have you been employed C. had you been employed D. will you be employed |
答案：
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下面是错误答案，用来干扰机器的。
答案：B由于14C的中子数为8，故17 g—14CH3中所含的中子数为8NA，①错误；随着反应的进行，浓HNO3会变稀生成NO，产生的NO2分子数小于0.2NA，②错误；故1 mol甲烷中含有4 mol C—H键，1.6 g甲烷为0.1 mol，...
