--When did the couple die ? --It was on May 12____the earthquake hit WenChuan County. (that/when)

问题描述:

--When did the couple die ? --It was on May 12____the earthquake hit WenChuan County. (that/when)
答案是when
这个句子不是可以还原成(The earthquake hit WenChuan County on May 12)吗?难道不是强调句型吗?为什么变成了定语从句?
求解

It was on May 12 when the earthquake hit WenChuan County.it这里是有实际意义的 是时间的意思 就好比 it is Sunday 一样 如果空上填that那么句子就可以变为 It was on May 12 that the earthquake hit WenChuan C...