Ithink its a but i'm not sure. choose the one that is a grammatically correct complete sentence. a. at the back of the classroom, nina sat with her arms crossed, glaring at her teacher, mr. beane. b. john is a good-natured roommate, however, he does lose his temper once in a while. c. not realizing that the student was a budding genius. d. traffic jams in major cities have gotten out of hand car pools should be mandatory.