The water is too cold for us to swim in.
翻译:水太冷,我们不能在里面游泳.
it是代词,是指代名词的,如果我们将it还原成the water,就显得重复,所以it是多余的.
He was too young to drive the car.
翻译:他年纪太小,还不能开车.
drive the car 表示“开汽车”,当然不能省略,因为前面是he,这里没有重复.
The water is too cold for us to swim in.
翻译:水太冷,我们不能在里面游泳.
it是代词,是指代名词的,如果我们将it还原成the water,就显得重复,所以it是多余的.
He was too young to drive the car.
翻译:他年纪太小,还不能开车.
drive the car 表示“开汽车”,当然不能省略,因为前面是he,这里没有重复.