在下列过程中，属于机械能转化为内能的是：[ ]
A.冬天用热水袋取暖
B.用水冷却汽车发动机
C.用酒精灯给水加热
D.陨石坠入大气层成为流星
答案：D
His efforts to raise money for his program were _____ because no one showed any intention to take
a cent out of their pockets. [ ]
A. in place
B. in vain
C. in effect
D. in advance
科技工程保险包括以下哪几类（）
A.卫星工程
B.长江三峡工程
C.海洋石油开发工程
D.核电站工程
