给你举个例子你就明白了:
It is three years since he smoked （他戒烟3年了）
It is three years since he began to smoke （他吸烟3年了）
It is /has been +段时间+since从句,从句中的动词如果为延续性动词就译为否定句,如果为瞬间性动词就译为肯定句.
给你举个例子你就明白了:
It is three years since he smoked （他戒烟3年了）
It is three years since he began to smoke （他吸烟3年了）
It is /has been +段时间+since从句,从句中的动词如果为延续性动词就译为否定句,如果为瞬间性动词就译为肯定句.