three years have passed since they met last time.为什么不是has passed ?表示时间的不是用单数吗?

I have been here for three years.=It is three years ______I____here I have known sandy since three years ago以 since three years ago ,提问 three years She have bought the computer since three years ago I have joined the club since three years ago How much have you grown in the last three years? 纠错 ---How soon have you lived here? ----For three years. He______this computer for adbout three years.用have怎么填 We have been in China for three years ago .改错 I have study English for three years?是什么时态 We have learned English for more than three years.We have learned English for _______three years. I have been collecting shells for three years.和 I have collected shells for three years.在语法和意 I have come to China for three years.为什么不是I have came to China for three years with the help of teachers,they have made great progress( )A three years agoB in the past three yearsC for three yearsD before three years I have been learning history for morethan three years (对划线部分提问for more than three years 划线 they have learnt English since three years ago.改为同义句____ three years ____ they started learning English. I lived here for three years和I have lived here for three years前者是对的,可是为什么? we friends sinece three years agowe friends sinece three years ago A are B have made C have been D have became 选那个