I believe living in the sea is the most practical and most realistic option. In order for a place to be suitable for humans to live, it must be able to provide most necessary resources. With that said, when you compare the three, the option that provides zero resources is other planets, because of all the planets we discovered, there is none that meets any of the requirements to sustain life, and whether we’ll ever discover a planet that does is unknown. 

托福口语真题：未来的人们应该住在哪里？

Next, when looking at Earth, the polar regions won’t work either, since they’re too devoid of resources. The harsh climate won’t allow us to grow enough food to sustain a population. The oceans and seas are a different story, however. Not only is the marine environment resource-rich, we could realistically expect future technology to solve the current problems.

我觉得住海里是最靠谱、最现实的选择。一个地方适合人类生活，它必须能够提供必要的资源。我们来比较这3个选择，其他行星上啥资源都没有，因为我们目前发现的所有星球没有一个能维持生命。谁也不知道我们能不能发现一颗能够让我们活下去的行星。再来看地球上，极地也不行，因为资源太少了。气候恶劣，我们没法种植足够的粮食来维持人口。然而，海洋就不一样了，海洋不仅资源丰富，而且未来的技术很有可能解决当前的问题。