Question

It_(be)Sunday,the library was closed.填being 能填was或is吗为什么，急，在线等

Answer 1

可以填was，表示两个分句，因为句子the library was closed.说明了是过去的事，所以前面也要用过去时态。It was Sunday,the library was closed.
It being Sunday, the library was closed＝As it was Sunday , the library was closed.
由于那是星期天，图书馆关闭了.
It being Sunday是独立主格结构，在此相当于原因状语从句。it在此题中表示时间。

Answer 2

不行，逗号不能分割两条语句，如果写was或者is的话，有了谓语就是完整的句子了，不合语法，所以填动名词，前面的动名词"句子"可以用来修饰后面的主句

Answer 3

此外，我英语四级考了6次才过，你看着办吧

Answer 4

reigners come to Si Chuan and Chong Qing to have a taste of the loca