I [ ]about visiting my sister ,but i have changed my mind这句话为什么不能填have thought?答案是thought,但为什么呢?

i tell you --- visiting the great wall.1,about something2,anyting about 3,something about.为什么要用visiting I am thinking about ___ some European countries.A.to visit B.are visiting C.visiting D.am visiting选哪个?为什么 I am visiting my what about visiting our teacher?意思 What about visiting the museum?[同义句] I'm visiting My friends I [ ]about visiting my sister ,but i have changed my mind这句话为什么不能填have thought?答案是thought,但为什么呢? What about visiting the Century Park tomorrow?(保持意思不变) ___ ___we visiting Century Park -I have heard bob ( ) from his journey to africa.-what about visiting him tonight?为什么()里要填“is back”而不是“come back? What about visiting the Great Wall（改为同义）句 visiting,what,about,your,sunday,aunt,this.连词成句 What about visiting the Great Wall?（改为同一句） 翻译 Then I read a longer passage in English about the delights of touring in Britain ,and another about the delights of visiting London ,and both were excellentand just right ,and I began to consider a job in radio I am visiting some of my old friends可不可以改为I am visiting my old friends I am going visiting.和 I am visiting.有什么区别? i`m visiting my aunt for vacation 对划线部分提问.划线部分：visiting my aunt I'm visiting my friends.(改为一般疑问句）_______ _______ visiting your friends? i with my parents_____my uncle in Hangzhou是is visiting 还是are visiting?为什么?