7-8 BBD
6. B 第二段最后一句是“月球人”提出的问题,现在人们正在考虑这一问题的可行性。
7. B 从文中 “Underground systems are already in place.” “Many cities have underground car parks.” “Many cities have underground car parks.” 和 “The Chunnel, a tunnel connecting England and France, is now complete.” 三句话可知答案。
8. D 短文提出了一个充分利用地下空间的问题:向地下发展。