I will never forget my【 experience--experiences】 during the shanghai Expo,【that--which】 has disturbed me a lot.it was a saturday noon 【but--and】 many visitors were having 【去除a】 lunch on the grassland.I saw a foreign couple and a Chinese couple who 【have--had】 just sinished their lunch.Without 【some--any】 hesitation ,the chinese couple threw their leftover food on the grass.【Astonishing--Astonishingly】,the foreign couple saig,"it's no good damaging the environment by littering carelessly."The 【word--words】 of the foreign couple struck my mind.It is time that we 【strengthen--strengthened】 our awareness of environmental protection.The phenomnon for spitting and littering in public places should【加be】 banned completely.