I was scared and feeling pretty anxious,this being my first time in a new country.为什么这里用this being?

I was scared and feeling pretty anxious,this being my first time in a new country.为什么这里用this being?
this being 是独立主格结构.请比较下面两句话的不同：
I was scared and feeling pretty anxious,this being my first time in a new country.
I was scared and feeling pretty anxious,and this was my first time in a new country.
I hope this book will be of some help to beginners of English.为什么用of some help?
这里be of help=be helpful
Professor Li's book will show you how what you have observed can be used in other context.为什么用how what you have observed 为什么how 和what一起用?这里不是how和what连用,而是这个句子可以分为几个层次.句子主干Professor Li's book will show you,其后用了一个how引导的从句作宾语从句,而这个how引导的宾语从句的主语又是由what引导的主语从句充当的.
The old man was so angry and spoke so fast that none of his children understood what what he said meant?为什么用what what?
这句中so...that引导了一个结果状语从句,在结果状语从句中understood的宾语是一个what引导的疑问句,而这个疑问句的主语则又是一个what引导的主语从句来充当,意为“他的孩子们没有一个理解他所说的是什么意思”.