The words that we should pay attention to_______on the blackboard.

The words that we should pay attention to_______on the blackboard.

– Do you know who cleaned the blackboard, Tina?

      -- Yes. John _____.

     A. do                          B. does                        C. did

— Why are you always standing in class, Kitty?
—I can’t see the blackboard clearly because the two tall boys are sitting
       me.