I was teaching an MDCAT prep class. I wrote an MCQ containing a grammatical problem and invited comments and responses from the class. 

Some of the students came up with their responses right away. Others were reluctant, wanting some encouragement. And there were yet others who were aloof, unwilling to come out of themselves. One of the girls, sitting by the wall, was particularly indifferent. I approached her and asked what she thought of the thing on the whiteboard. She hesitated for a moment and then answered my question.