When to Use “你(nǐ)” And “您(nín)?”

Lǎoshī, __ hǎo! Student:老师,    __ 好!                 Hello, teacher!

                __ hǎo! Teacher:__ 好!

                Hello!

A. 你(nǐ);您(nín)

B. 您(nín);您(nín)

C. 您(nín);你(nǐ)