This procedure ensures correct placement of the catheter.

这个程序可保证导液管的正确置入。

Natural selection ensures only the fittest survive to pass their genes on to the next generation.

物竞天择确保只有最适应环境的物种才得以生存下来，把基因传递给下一代。

The humidity of the bathroom ensures that it grows well.

浴室的湿度能确保它生长良好。

It controls the traffic lights and ensures the safety of the people getting in and out of the stadium.

它控制交通灯，确保获得进出体育场馆的人群安全。

"Yes, but it is a chain, friend, which ensures you the blessed bread of existence," answered the poet.

“是的，不过这是一条锁链，朋友，它能确保你有面包吃。”诗人回答说。