—Dad,I’ve finished my assignment.—Good,and__________you play or watch TV,you mustn’t disturb me.
One way to understand thousands of new words is to gain _____ good knowledge of basic word formation.
--Do you know anyone in Paris? --No, I’ll make friends once______ .
The research is so designed that once ______ nothing can be done to change it.
He is always______fault with other people though he doesn’t do his own work properly.
Meeting my uncle after all these years was an unforgettable moment, ____ I will always treasure.