51. decision on/against 做/不做……的决定，如：

　　A decision on this matter is pending.

　　此事即将作出决定.

　　The committee reversed its decision on import quota.

　　委员会取消了对进口货物的配额的决定。

　　52. decrease in sth ……的减少，如：

　　A decrease in signal power as measured between two points.

　　信号能量在两点间测量出来的减小量。

　　There has been a steady decrease in population in this city.

　　这个城市的人口在持续下降。

　　53. defence against 防御,保卫，如：

　　Trees are a defence against the wind.

　　树是一种防风物。

　　The country put up a strong defence against the enemy 's invasion

　　为了抵制敌人的侵略,这个国家布置了坚固的防御工事

　　54. delegate to 参加……的代表，如：

　　He was elected as a delegate to the annual conference.

　　他被选为年会代表。

　　55. demand for 对……的需求，如：

　　Demand for hospital services remained high.

　　居民对医院服务的需求仍然殷切。

　　A fall in demand for oil tankers has put/placed thousands of jobs in the shipbuilding industry in jeopardy.

　　油轮需求量下降使造船业成千上万的工作职位受到威胁.