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 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

问题：

1 C中省略了is，可以么？因为前面已经有个are，那根据and的省略原则，前面有be 动词，后面的be动词不是也应该省略么？

2 C中的or else与B中的were it to do so ，两个短语的具体用法哪位NN可以指点一下呢？谢谢了

主语和谓语都相同时，才可以同时省略，这里主语不同，谓语不可以省略。

or else不但是口语，且这个else是多余的。