请教 GWD-9-Q27

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.

1. and, if it strikes Earth, it can do tremendous damage to part of the planet but

2. and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would

3. and that, if it were to strike Earth, could do tremendous damage to part of the planet but would

4. and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would
5. and that, if it strikes Earth, it could experience a tremendous amount of damage but

答案是C，偶有点疑问，特别是C里的“if it were to strike Earth.."，be to do sth不是GMAT语法错误的标志吗？

哦。。。原来是两个that并列呀。。。谢谢指导

顺便再提一下，关于be to do sth, 我听到的说法是因为这是一个很主观的表达方法，就跟be going to do一样，所以在GMAT中一定是错误的，因为GMAT中一定要是客观陈述的书面语。而不是因为简洁不简洁的问题。

不过在这题里，相比之下好像也只能选C乐

以下是引用LuckiPanda在2007-7-21 11:00:00的发言：

E it 有歧义，无法确定是指earth or asteroid会受伤害

同一句话中的相同代词不是要指代同一个东西吗？怎能会有歧义？