boot是不是可数名词

　　The ski had become disconnected from the boot.

　　滑雪板与靴子脱离了。

　　Your boots are covered in mud.

　　你的靴子上都是泥。

　　The skis should detach from the boot if you fall.

　　要是你跌倒了，滑雪板就该脱离靴子。