科学家们正在研究气候变化对全球海洋的影响。

Scientists are studying the impact of climate change on the world's ___seas.

北海以丰富的渔业资源而闻名。

The North ___Seas are famous for their abundant fishery resources.

他站在演讲台上，面对人山人海的观众。

He stood on the stage, facing a ___sea of audience.