GWD 19-27 If it were to... - ChaseDream

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.

and, if it strikes Earth, it can do tremendous damage to part of the planet but>>
and, if it would strike Earth, part of the planet could experience a tremendous amount of damage but it would>>
and that, if it were to strike Earth, could do tremendous damage to part of the planet but would:
and that, if Earth is struck by it, can do part of the planet tremendous damage, but it would: it no zhidai >>
and that, if it strikes Earth, it could experience a tremendous amount of damage but : experience awkward

做题的时候选对了，现在看的时候又糊涂了

我记得og 上有 if 的考点，都是考：if x happens, then y will happen. or y will happen only if x happens. IF 句子跟的总是现在时，上题中用了 WERE TO 结构，我忘了 WERE TO 这个语法点了，也没查到，还请大家帮忙，这里是不是因为是个ASSUMPTION，所以用了虚拟？

我看到的IF WERE TO 的结构有： If I were the priminister, or If you were president. 说明都是不现实的东西，而这里科学家have identified .也适用虚拟马？

谢谢

1. Many economists predict that the next recession, when it comes, will be caused by Federal Reserve action taken to prevent an inflationary upsurge that would result if the economy were to expand at an annual rate of three percent or more.