.People who do not smoke have less ____________ of suffering from lung cancer than those who do so.
—Is there any vaccine(疫苗) against H1N1 flu that can be used on humans? —No, but scientists are working to develop ________ .
Betty, still ______ excited, took away the box ______ with birthday presents for her.
--- I think it necessary that he _____ to New York but to London. --- I agree, but the problem is _____ he has refused to.
you be interested, I’ll tell you the whole story.
--You look upset. Anything wrong? --I failed in the physics exam again _____all the efforts I made.