问题
选择题
| — Where did you pick up this wallet? — _____ in the supermarket. |
| A. That was B. That is C. It was D. It is |
答案
答案：C
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| — Where did you pick up this wallet? — _____ in the supermarket. |
| A. That was B. That is C. It was D. It is |
答案：C
圆弧轨道，BC段为粗糙水平面，滑块从A点由静止开始下滑，在水平面上运动了1.6m后停止于C点。己知弧形轨道与水平轨道相切，空气阻力不计。取g＝10m/s2，