One learns a knowledge by making mistakes and ______ them

My book was here a second ago but now it’s missing. Someone ________ a joke on me.[ ]

I failed in the examination last term and only then ____ the importance of studies.

It is a shopping mall ______has been built in ______ used to be a school.

What a nice T-shirt! How much did you_____ for it –It_____ me twenty yuan.