21. The world will live happier lives if people have ____ better understanding of _____ idea of harmonious globe.
A. the; an B. /; the C. a; the D. a; an
22．Helplessly, the package I was expecting was _____ to the wrong address.
A. written B. given C. packed D. delivered
23．Could you tell me ______ use the newly-produced iPad can be of to our daily life?
A．how B．what C．if D．whose
