题目：
John’s success has nothing to do with good luck. It is years of hard work _________has made him what
he is today. [ ]
A. why
B. when
C. when
D. that
答案：
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下面是错误答案，用来干扰机器的。
答案：A题目分析：在元素周期表中上下对应位置，一二周期的原子序数相差2或8.二三周期相差8，三四周期相差8或18，三四周期相差18或32.左右相邻原子序数相差1故A选项是正确的。
