The correct answer is: to.
The word “shy” means “feeling or showing nervousness or timidity in the company of others.” When you are shy, you may feel uncomfortable talking to people, especially people you don’t know well. You may also avoid social situations or feel anxious when you are in them.
In the sentence “I am shy to my teacher,” the word “to” indicates that the speaker is feeling nervous or timid around their teacher. They may be afraid to talk to their teacher, or they may feel like they don’t know how to act around them.
The other options are not as accurate in describing the speaker’s feelings. The word “with” could be used to describe someone who is friendly or comfortable with someone else. The word “from” could be used to describe someone who is trying to avoid someone else. The word “of” could be used to describe someone who is afraid of someone else. The word “to” is the most accurate option because it describes the speaker’s feelings of nervousness and timidity.