英语The important thing is to keep the earth clean.这句话为什么用to keep,而不用keeping?

the thin blue 英语thin怎么读 thin英语怎么读 The important of health 英语作文 英语的最高级,比较级怎么变型,如：big bigger biggest/important more important the most important 英语important Perhaps the most important part of being beautiful in Hollywood,is to be thin中文意思,part of being 在这儿是什么意思和什么词性 The explanation is pretty thin. 问英语问题,the+形容词与 the + 形容词+ 名词的区别例如说the important，和the important exam 英语作文：what is the most important ni your lift 英语作文The important of numbers 60字的 初中生英语作文大全the lnternet is important to us 英语作文：why the friendship is important for us Which meal is the most important?用英语回答 the important of multicultural knowledge求一篇英语作文 以The most important in ventions的英语作文 The ( ) is thin,the( ) is thick. the wrong side of the thin edge