If you want to do the experiment again, you had better be more careful_______ you made a mistake.
I love to buy a new dress at a _______ at the Spring Festival.
I don’t know whether you happen ____ that he has been away for two months.
The two sportsmen congratulated each other ____ winning the match by shaking hands.
It ____ we had stayed together for a couple of weeks_____ I found we had a lot in common.
---I think sometimes watching TV will cause visual pollution to the teenagers.---_________.