5. In our class, when the bell rang and the taacher closed his book, it was a        or everyone to stand up.

There are hundreds of visitors ___ in front of the Art Gallery to have a look at Van Gogh’s paintings.

It is widely accepted that animals learn to do things because their certain acts lead to _______.

Tom’s little sister is a girl of great _______. She takes an interest in everything.

My trousers are too old.I’ll have to buy ____.