题目

One morning, the door to the classroom opened and a new teacher, Mrs Cosby, walked in. She looked too_______to ever deal with us. And we sure gave her a___________time, but she never lost her temper. And then came the last day of the first month she had been our teacher. She___________some papers the moment she entered the classroom. We_______the worst — a test. But no, it was something that totally_________us.Mrs Cosby asked us to come to the front of the class, and gave each of us a piece of___________, on which she had written what the student with_________ had been good at during the las若ab=1，则1a2+1+1b2+1的值为（　　）A．1B．-1C．12D．2