be at suck

例句：

1. 1. The baby was sucking on the bottle greedily.
   宝宝贪婪地吮吸着奶瓶。
2. 2. The dog was sucking on a bone as it lay down.
   狗躺在地上，正吮吸着骨头。
3. 3. The air is sucked out of the balloon as it rises.
   随着气球上升，空气被抽走了。