2. The helicopter made a slow arc, passing over the mound but not stopping. 这架直升飞机做了一个缓慢的弧线运行，飞过那座小丘，但没停下来。
3. That's one reason why we have launched Arc, a new publication dedicated to the near future. 这就是我们推出 Arc 的原因之一，因为这是一份为不久的将来而创造的新出版物。
4. Unlike the original form used in early pendulum clocks, the anchor escapement permitted the pendulum to travel in a very small arc. 与在早期摆钟中使用的原始形式不同，锚擒纵装置允许钟摆沿非常小的弧线运动。
5. As one hemisphere of Earth tilts farther from the sun, the arc of the sun's daily path seen from that location lowers toward the horizon. 当地球一个半球距太阳的倾斜度更大时，从那个位置看到的太阳每日运行轨迹的弧线就会向地平线下降。
