Without its solid platform, they can't hunt the seals they need in order to survive.

没有坚实的冰作为平台，北极熊就不能猎捕它们赖以生存的海豹。

He built a solid platform over the well, and a heavy cover for the hole that let the water-bucket through.

他在井上搭建了一个坚固的平台，并为让水桶通过的洞盖了一个厚重的盖子。