could

When I was ten years old, I could swim across the entire lake.

(Chinese) 我十岁的时候，能游过整个湖。

She could speak three languages fluently before she graduated from college.

(Chinese) 她在大学毕业前就能流利地说三种语言。

It could rain this afternoon, so you should bring an umbrella just in case.

(Chinese) 今天下午可能会下雨，所以你最好带把伞以防万一。

Could you please pass me the salt from the other side of the table?

(Chinese) 你能把桌子那边的盐递给我吗？