You never know how much difficulty we had _________________ the problem. Luckily, we try to solve it with Mrs Wu’s help.

Physical Education in schools can teach us endurance — something we all need ______ life becomes tough

Was it in the street _____ you met her? [ ]

Whose money is this? — Just leave it it isIt doesn’t belong to us

In a harmonious society,we’d better prevent pollution _______ happily. [ ]