Cordial greetings to the teachers , not the extrapolite, which embodies respect for others.
这一句亲切的问候，并非多余的客套，它体现了对他人的尊重。
2
You smile because you are happy. You smile because it releases those endorphins that bring you extra happiness. You smile at others because it is polite and friendly (and you are glad to see them).