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 answer : B

这题以前没人问过，可我实在不明白为什么选b。要考了，急啊。请nn们指教