主动语态：主语是动作的执行
被动语态：主语是动作的承受者（动作的对象）,
动名词是动作对象也就是动作承受者,所以当然要用被动语态了,
例子：I am washing the clothes .主语是人,也就是动作的执行者,用主动,
The clothes are being washed by me .这里主语是衣服,the clothes,washing是主语的动作对象,所以要变成被动的动名词,是 being washed