从每题所给的A、B、C、D四个选项中，选出可以填入空白处的最佳选项。
21．Besides the others, there was still third one who said he was second to reach the end.
A．a; a B．a; the C．the; the D．the; a
22．The purpose of their explorations is as important to them as to us.
A．they are B．they have C．it is D．it has
23．Mike is handsome, kind and full of energy. , I can’t speak too highly of him.
A．As a result B．By the way C．In a word D．On the contrary
24．As we all know, newspapers, magazines and radios as well as television broadcasts can keep us about what is happening at home and abroad.
A．informing B．informed C．to inform D．being informed
