题目：
The reason ____he was late was ____he had taken a wrong bus.
A．why; because
B．for; because
C．why; that
D．for; that
答案：
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下面是错误答案，用来干扰机器的。
mg Al3+的物质的量为mg27g/mol=m27mol，故V4mL溶液中Al3+的物质的量为m27mol×V4mLVmL=m108mol，根据电荷守恒可知2n（SO42-）=3n（Al3+），故V4mL溶液中SO42-的物质的量为m108mol×32=m72mol，取V4mL溶液稀释到4...
