动词时态标志词 1.一般现在时
(1) always, usually, often, sometimes
(3) in the morning, on Saturdays
(4) once a week, three times, a day, twice a year
(1) yesterday, the day before yesterday, yesterday morning (evening, afternoon)
(2) last time, last Friday, last term, last month
(3) 2 hours ago, a week ago, 3 years ago