title: 帮忙选一下，并解释一下涉及的语法问题It____nowprett 
desc: It ____ now pretty late, we took our things and retir to our room.　　    A) is       B) being        C) turned        D) got 
answer: B) being 
  独立主格结构,因为后面的句子主谓宾已经齐全,所以前面的不能是正常的句子,即谓语得用动词的非谓语形式,所以把was换成being.