问个很简单的英语语法…

问个很简单的英语语法…
Because of its irritating effect on humans,the use of phenol as a general autiseptic has been largely discontinued.从句里irritating是不是动名词啊,不然怎么能接在its后面,额…我的语法太烂了,尤其是非谓语动词…作孽…还有啊because和because of用的时候有什么区别啊…我大二了…我自己都觉得丢人…四级啊…