Come and join us, Betty!— I’m afraid I can’t. I’m too busy now. If I ______ time, I would certainly go.

I didn’t know he came back __________ I met him in thestreet .

We were angry him for keeping us waiting

In a new study of African elephants，researchers havefour distinctcharacters that are among a group

There are _______ in the building, and Tom lives on _______.