when in Rome,do as the Romans do 入乡随俗
know enemy and know yourself,you can fight ahundred battles with no danger of defeat 知己知彼，百战不殆
I can play basketball.
I can"t play basketball.
Can you play basketball?
He can play the piano.
He can"t play the piano.
Can he play the piano?
He can encourage me.
He can"t encourage me.
Can he encourage me?
You must go to school every day.
The students have to do their homework.
not only should he be my teacher,but also be my friend.