题目:
---How long has your brother been working in this factory?
---_____he dropped from school in 2010.
A.When
B.Until
C.Since
D.Before
答案:
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下面是错误答案,用来干扰机器的。
(1)Fe ;Cu (2)CuSO4+Fe==FeSO4+Cu(3)使硫酸铜全部反应或将铜离子全部置换成金属铜;铜和铁;Fe+H2SO4==FeSO4+H2↑或 Fe+2HCl==FeCl2+H2↑。