may,might,could,should可能性比较

2.can & could 我们用can来表示“知道怎么做...”或者“对某人来说,...是可操作的”。 i can play guitar, but i can't play piano. 我会弹吉它,但是我不会弹钢琴。 canyou swim? --yes, but i'm not a very