---Why didn't you go to the party last night?---Because I was waiting for Sam in his office _______ he came back.
Sam with his friend Helen _______ in Class Three. They are in Class One.
It’s important ______ people to understand each other.
Bob is _______ an English class. His teacher is talking ________ English.
— ________ your friend? —The boy in front of the old man.
Yingying often _____ hamburgers, French fries and Coke and her mother often cooks _______ Chinese food for them.