I can’t say which sofa looks better. It’s just a (an) _____ of personal preference.
---Can you tell me Sam’s telephone number? ---_________.Who is Sam? The newcomer?
The three teams _____ different ways to solve the problem and they all succeeded at last.
The band was very successful in the seventies, most of _____ members were in their twenties.
---Did you enjoy yourself in Hefei this summer? ---________ It was too hot.
Every year _____ money are spent on environment protection.