（）the sky gets dark,it is going to rain soon.
1since 2 because 3 as 4 for
答案选3 as
conj.因为；随着
翻译：随着天变黑,快要下雨了.
（）every thing is ready ,let's begin our meeting.
1since 2 because 3 as 4 for
答案选1since
在这里since是既然的意思!
翻译：既然都开始了,就让我们开始会议吧!