drop center wheel

例句：

1. 1. The sun dropped below the horizon.
   太阳在地平线以下落下。
2. 2. She dropped her phone on the ground and stepped on it.
   她把手机掉在地上，踩到了它。
3. 3. The raindrops fell gently from the sky.
   雨滴从天空中轻轻落下。