看过来,这个ing是动名词还是分词

问题描述:

看过来,这个ing是动名词还是分词
The air keeping the balloon up was escaping quickly and the balloon was coming down.这个句子里keeping是动名词还分词,什么成分,

keeping 是分词,keeping the balloon up 是后置定语,修饰 the air
也可以写成:the air that keeps the balloon up was...
全句:使气球保持在空中的空气正迅速泄漏,气球正向下落.