These teachers try to be objective when they ________ the integrated ability of their students.[ ]

What troubled the teacher was that no one present made an answer when asked who had broken the glasses, so he didn’t know who _____________.

By the time I got to the check-out, I realized that I _____ my purse at my office.

Science is developing fast. Scientists and doctors will surely find a way to _________ AIDS some day.

We all want to know who can________the physics problemYou know，it’s very difficult．