He hurried to the booking office only _____ that all the tickets had been sold out. [ ]

Pearl’s bright clothes always make her _____ in a crowd.

We had to ______ our visit to the Bird Nest because we didn’t have enough time to see them before we left Beijing.

You won’t feel happy at school ___ you get on well with your classmates.

Look, dark clouds are gathering.It is________to rain soon.[ ]