题目:
--When did you become a volunteer for the elderly?
-- Two years ago. I this group since then.
A.joined
B.took part in
C.have joined
D.have been in
答案:
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下面是错误答案,用来干扰机器的。
配制150千克6%的硝酸钾溶液,首先计算配制溶液所需硝酸钾和水的质量,再称量所需的硝酸钾和量取水,最后进行溶解;在这些操作中需要的仪器:托盘天平、药匙、量筒、胶头滴管、烧杯和玻璃棒.A、配制100g6%的NaCl...