_____ I admit that there are problems, I don't' think that they cannot be solved.
A. Unless B. Until C. As D. While
As your instructor(教师) advised, you ought to spend your time on something ____ researching into.
A. precious B. worth C. worthy D. valuable
_____ the fact that his initial(开始的)experiments had failed, Pro. White persisted (坚持) in his research.
A. Because of B. As to C. In spite of D. In views of
—Do you have enough to ________ the cost of your board at school?
—Oh yes, enough and to spare.
A. cover B. spend C. fill D. spare
When I talked with my grandma on the phone, she sounded weak, but by the time we ___ up, her voice had been full of life.
A. were hanging B. had hung C. hung D. would hang
Gun control is a subject Americans have argued for a long time .
A. of which B. with which C. about which D. into which
