[求助]GWD4-28

xiao_zhutou

Antarctica receives more solar radiation than does any other place on Earth, yet the temperatures are so cold and the ice cap is reflective, so that little polar ice melts during the summer; otherwise, the water levels of the oceans would rise 250 feet and engulf most of the world’s great cities.

is reflective, so that little polar ice melts during the summer; otherwise,

is so reflective that little of the polar ice melts during the summer; were it not to do so,

so reflective that little polar ice melts during the summer, or else

reflective, so that little of the polar ice melts during the summer, or

reflects so that little of the polar ice melts during the summer; if it did

这道题太晕啦--- were it not to do so 怎么讲啊？？按照虚拟语气还原成正常顺序，应该是 " if it were not to do so"。这里的"it" 指什么啊？为什么用"be to do so"的结构啊？？晕晕晕

hitler999

it 应该是指代的do so吧