valid: implies being supported by objective truth or generally accepted authority: absence will be excused for ~ reasons.     （supported by符合）    （authority译作准则较好）


sound: implies a basis of flawless reasoning or solid gounds: a ~ proposal for combatting terrorism.   solid坚实的，两个词发音相近，可谐音记忆  


cogent: may stress either weight of sound argument and evidence or lucidity of presentation: the prosecutor's ~ summation won over the jury.     (weight of sound argument and evidence论证有力)  (lucidity of presentation表达清晰)  summation总结概括


convincing: suggests a power to overcome doubt, opposition, or reluctance to accept: a documentary that makes a ~ case for court reform.


telling: stresses an immediate and crucial effect striking at the heart of a matter and may or may not imply soundness and validity: a ~ example of bureaucratic mentality.    (may or may not imply soundness and validity不一定完全正当合理)


valid正当: 符合客观事实和公认准则，sound合理: 基于无瑕的推理和坚实的依据，cogent有力的: 论证有力、表达清晰，convincing让人信服的: 能克服疑虑反对犹豫，telling说明问题的: 直接击中问题核心要害


记忆方法: 1) 首字母CCS常常上、TV电视，常常上电视<==因为合理

         2) 合理的意思是令人接受的mean having such force as to compel attention or acceptance.首字母CCS常常上、TV电视，常常上电视<==因为合理