15. present perfect with for and since(for&since와 함께 쓰이는 과거완료) ① Form * 단순 과거 : I started studying here five years ago. * 단순 현재 : I study here now. * 과거 완료 : I've studied here for five years. Not I am studying here for five years. * 단순 과거 : I met Tom for the first time in 2007. * 단순 현재 : I stell know him. * 과거 완료 : I've Known..