21． To make members of a team perform better, the trainer first of all has to know their ______ and weaknesses．
A． strengths B． benefits C． techniques D． values
22． The medical reform in that country proved to be _____ failure, but as we know, success often comes after _____ failure．
A． a; the B． a; / C． a; a D． /; /
23．________by the advances in technology, many farmers have set up wind farms on their land．
A． Being encouraged B． Encouraging C． Having encouraged D． Encouraged
