题目

“它提供了治理和利用热能,为机械供给动力的手段。因而,它结束了人类对畜力、风力和水力的由来已久的依赖”。这是对哪一发明的描述? （    ）A. 发电机    B. 纺纱机     C. 电动机    D. 蒸汽机 答案：D--- Look at these stamps. I _______ them for five years.--- Wow, they are beautiful.A. bought B. have boughtC. kept D. have kept