____ caused the accident is still a complete mystery.
The little boy ,out of curiosity ,_______the toy to see how it worked ,but couldn’t put it together .
They have always treated us with open hands and we must be generous _______.
The chief editor expressed his doubt _______senior people would enjoy reading such magazines .
As your instructor advised ,you ought to spend your time on something ______researching into .
Fancy Williams not ______the answer to such an easy question !