英语 since 用法Sometimes I think I wouldn`t .But since having been here ,I have to accept it ,there being no way .since 在表 “既然”时后面接句子才对,这句后接动名词应该是错误的?But since I have been here It is right

since
A) ad.(常用於现在完成式或过去完成式)
1.此後;从那时到现在
e.g.She left school three years ago and has worked as a nurse ever since.她三年前毕业,从那时起便一直当护士.
2.之前,以前
B) prep.
1.(常用於现在完成式或过去完成式) 自...以来,从...至今
e.g I haven't heard from him since last year.
我自去年以来未曾收到过他的信.
C) conj.
1.(常用於现在完成式或过去完成式) 自...以来,从...至今
e.g.It's been ten years since they married.
他们结婚到现在已经十年了.
e.g.She has been living a hard life since her husband died.
自从丈夫死後,她一直过著艰苦的生活.
2.既然;因为,由於
e.g.He must have taken the book since it isn't here.
他一定是把书拿走了,因为书已不在这里了.
e.g.Since it is so hot,let's go swimming.
既然天气这麼热,我们去游泳吧.