[求助]TT GWD-7-18

Q18:

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.

1. is reflective, so that little polar ice melts during the summer; otherwise,
2. is so reflective that little of the polar ice melts during the summer; were it to do so,
3. so reflective that little polar ice melts during the summer, or else
4. reflective, so that little of the polar ice melts during the summer, or（B）
5. reflects so that little of the polar ice melts during the summer; if it did

我觉得B选项中的it指代不明啊

分句中只有一个V,所以do指代谁肯定不回错,所以it也是

C与前面平行的话少了个be

但是这里前面一个分句太复杂，B里面的so到底指什么情况呢？因为总不可能指代整个分句了吧？如果不是指代整个句子，后面的结果就不能正常推导出来。何况C里面的be是可以省略的。GWD7的第一题就是：

So dogged were Frances Perkins’ investigations of the garment industry, and her lobbying for wage and hour reform was persistent, Alfred E. Smith and Franklin D. Roosevelt recruited Perkins to work within the government, rather than as a social worker.

1. and her lobbying for wage and hour reform was persistent,
2. and lobbying for wage and hour reform was persistent, so that
3. her lobbying for wage and hour reform persistent, that
4. lobbying for wage and hour reform was so persistent,
5. so persistent her lobbying for wage and hour reform, that

   Answer:  E