always(总是),usually(通常),frequently（经常） often （经常）sometimes(有时),seldom(不常),rarely（极少）,never（从不） once(一次),twice(两次),等.
all the time 100%；
almost ,always 90%；
generally ,usually 80%；
often ,frequently 60-70%；
as often as not 40-50%；
sometimes ,at times 20-30%；
occasionally ,from time to time 10%；
hardly ,seldom ,rarely 5%；
never 0%.