foot复数形式是什么

Your feet must be behind the line when you serve.

发球时你的'脚必须站在底线的外面。

She shifted her weight from one foot to the other.

她把身体的重量从一只脚换到另一只脚上。

It was the first time I had set foot on American soil.

那是我第一次踏足美洲大地。

You can back up another two feet or so.

你可以再退两英尺左右。

It was the first time I had set foot on African soil.

那是我第一次踏上非洲大地。