______ many times, he finally understood it.
When the food in the hotel where we are staying , what should we do?
Since you understand all this, is no need for me to explain.
—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.