题目选项分析

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

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