一个物体以某一初速度从固定的粗糙斜面底部沿斜面向上滑，物体滑到最高点后又返回到斜面的底部，则下述说法中正确的是（ ）
A．上滑过程中重力对物体做的功与下滑过程中重力对物体做的功相同
B．上滑过程中摩擦力做功的平均功率等于下滑过程中摩擦力做功的平均功率
C．上滑过程中合外力做功的大小等于下滑过程中合外力做功的大小
D．上滑过程中机械能减少量等于下滑过程中机械能减少量
答案：D
| 从A--G中选出可以填入对话空白处（16-20）的最佳选项， 并将其字母序号填入题前的括号内。 选项中有两项为多余选项。 | |
| ( )1. A: This one looks great! __________ B: Me too.The sun … the sand…the ocean! ( )2. A: __________ What do you think of sailing, swimming,windsurfing, and fishing? B: Oh, Tom! They sound fantastic. I really like all those things A: Yeah…me, too. ( )3. B: __________. To be honest, I hate fishing, but I love all the others. ( )4. A: Hey! Look at this! We can stay in a big hotel or __________ B: You know, I really don't like those big hotels. ( )5. A: __________ Let's stay in a cabin. It'll be much nicer right beside the ocean.
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