being Sunday the library was closed.A. ThatB. It isC. ItD. This

问题补充：

being Sunday, the library was closed.

A. That

B. It is

C. It

D. This

答案：

A. That

B. It is

(答案→)C. It

D. This

解析：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。