全球气温上升会使
A．热带地区更加干旱
B．土地沙漠化进程加快
C．自然灾害越来越频繁
D．以上都会出现
答案：D
选择水源时，须综合考虑哪些原则？
It took __________ building supplies to construct these energy-saving houses. It took brains, too. [ ]
A. other than
B. more than
C. rather than
D. less than
