海豚用鼻子顶着球，使其保持平衡。
由Denis Oh设计的创意书架，你必须设法使其保持平衡。
Creative shelf that you have to balance designed by Denis Oh.
通过吃掉老弱病残和受伤者，鲨鱼协助维持其猎物鱼群的基因健康，同时也使其数量保持平衡。
Sharks help maintain the genetic health of the fish populations they feed on by eating the weak, sick and injured. They also keep their prey populations in balance.
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