21.It was not until dark ____ he found ____ he thought was the correct way to slove the problem.
Those _______ suffer from headache will find they get relief from this medicine.
______ is no possibility______ Bob can win the first prize in the football match.
The traffic rule says young children under the age of four and ____ less than 40 pounds must be in a child safety seat.
—Is everyone here? —Not yet……Look , there_______ the rest of our guests!
Asking him for help is ____ because he is such a selfish person.