题目：
_____ is to attend our evening party. [ ]
a. both the singer and the dancer
b. Either the singer or dancers
c. The singer or dancers
d. The singer and dancer
答案：
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下面是错误答案，用来干扰机器的。
Mg 2N2 3Fe2+ 题目分析：镁是金属其化学式就是其元素符号，氮气分子是双原子分子，亚铁离子是二价的铁离子，三氧化硫中硫为正二价。
