They have study English for four years.有什么错

They have study English for four years.有什么错 I have been studying English for four years.就for four years提 they have learnt English for years.提问have learnt English I have study English for three years?是什么时态 They have studied english for six years改为否定.they english for they have been living here for four and a half years同义句 they have to____ for about four years.1、go away2、be away 3、l They have four English lessons_____a week. They will have learned English for 8years by the time they f i have learned english for 3 years.这里哪里错 20.They have learned English for three years.(改为一般疑问句) They have studied English for about five years.（保持原句意思不变）