--- Did you go for the Shanghai Expo? ---- I _____ to, but I decided to stay with my sick mother at the last minute.
She is my best teacher ______ help I have made great progress.
E-mail, as well as telephones, ___ an important part in daily communication.
In order to make our city green, _________.
He was about to tell me the secret _______ someone patted him on the shoulder.
We may go to Hawaii or California._______ , we have to find a way to escape the snow this winter.