再问GWD-9-27，为何不选B，多谢

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.

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

Why not B? the answer is C

If choose B. part of the planet与不能an asteroid, 2000 BF19, that is a...平行。只能与主句Scientists have identified 平行。改变原文的意思。而且B中的it 指代不清。

Choose C      2000 BF19, that is about half ...and that  and that( ,if it were to strike Earth, )could do tremendous damage to part 结构正确，而且if it were to strike Earth用了正确的语态。

补遗

虚拟语气

  1)表示与现在的事实相反:从句的谓语动词用过去时(be一律用were),主句用should(第一人称)/would(第二、三人称)/could/might + 动词原形  例:They assumed that  if they did not hold it, their grip on Algeria would be always insecure

  2)表示与过去的事实相反:从句的谓语动词用had + 过去分词,主句用should(第一人称)/would(第二、三人称)/could/might + have + 过去分词

  3)表示与将来的事实相反:从句的谓语动词用should + 动词原形,主句用should(第一人称)/would(第二、三人称)/could/might + 动词原形

恩，接ＬＺ宝地留言，我现在ｐｒｅｐ１　一题要１分１５秒才Ｏｋ，还没有达到主要排除和次要排除的程度。那样可能速度就快乐。

If it were to strike earth是插入语。
            划线部分that从句与前面未划线部分并列that不可省略