October 1, 2009 is a special day, ________ I think, that will be remembered by all the Chinese forever.
The doctor will not perform the operation ___ it is absolutely necessary.
Difficulties are nothing ___ we are not afraid of them.
―When do we need to pay the balance ? ― September 30.
I'd like to go swimming ____ the water is not too cold.
It’s quite me why such things have been allowed to happen.