PREP08 246 关于定语从句平行

Gracespa

Scientists have identified an asteroid, 2000 BF19, that is about half a mile wide and, if it strikes Earth, it can do tremendous damage to part of the planet but probably not cause planetwide destruction.
A.    and, if it strikes Earth, it can do tremendous damage to part of the planet but
B.    and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would
C.    and that, if it were to strike Earth, could do tremendous damage to part of the planet but would
D.    and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would  
E.    and that, if it strikes Earth, it could experience a tremendous amount of damage but

答案C。定语从句的平行。
问题： and后面的that从句，怎么理解为是asteroid的定语从句呢？

haze619

不知道对不对，我是这么想的
and前面没有逗号，所以后面的从句主语应该还是an asteroid

而且主语省略，所以ABE可以排除掉了。。c  d的区别应该挺明显的了

Gracespa

感谢楼上的回复 被你这么一说我理解了一部分 是不是把if从句拿掉看会比较容易理解呢？ 这样就成了 and that could~~ 很明显如你所说地省略了主语？

haze619

恩恩，if那里你可以看成是个插入语

chipmunk

C the planet 指代 earth。这样才顺眼，看了半天有点纠结，应该懂点地理