31. reduction=decrease=drop=fall=cut n.减少
32. class=type=kind=sort=style=category=variety n.种类
33. rehearsal=practice=training=run-through=exercise n.排练，演习
34. peer=your peers are the people who are the same age as you, or who have the same type of job, social classetc n同伴.
35. defensive=used or intended to protect someone or something against attack n.防御
36. strategy=way=method=approach=technique=system=tactics n.方法，功略
37. assist=help=aid=with the aid of v.帮助
38. specific=give (somebody) more details=expand on=enlarge on=go into more=greater detail=be more specific=be more explicit=elaborate adj.特定的
39. substance=a particular type of solid, liquid, or gas n.物质
40. surroundings=environment=circumstance n. 环境
