The chairman thought________necessary to invite Professor Smith to speak at the meeting .

 — It is a pity that we have nothing to refer to when we come across new words.— I quite agree with you. There isn't any dictionary around when we need ______.

I can’t stand _______ when people litter around in public places.

We shouldn’t take_____ for granted that our parents will take care of us forever.

As a student, I’d prefer _______ if I didn’t have to do so much homework.