Scientists say it will be five or six years _____ it is possible to test this medicine on human patients.

Whether at school or at home, children should be encouraged to read books and ______ what may be useful to their study.

s section, we will briefly describe possibleways of reducing the costs and risks ______ in doing this.

are in trouble , Mike is always willing to_______ a hand

Howcold it is! We’ve never had ______ this winter.