thanks, thank you

[Ju]

• teacher or parents, "This is your cup of tea."
• student or children, "Thanks."

1. As the above conversastion, is it an impolite way for a student or children to say thanks only to a teacher or parents?
2. Can a staff say thanks only to a boss, is it too casual?
3. In a very formal situation, shall I say, "Thank you very much, I apprecate that." to express gratitude to all aspects? If not, how shall I say?

Thank you.
(any grammar mistake in this message?)

[MikeNewYork]

Originally Posted by Ju

• teacher or parents, "This is your cup of tea."
• student or children, "Thanks."

1. As the above conversastion, is it an impolite way for a student or children to say thanks only to a teacher or parents?
2. Can a staff say thanks only to a boss, is it too casual?
3. In a very formal situation, shall I say, "Thank you very much, I apprecate that." to express gratitude to all aspects? If not, how shall I say?

Thank you.
(any grammar mistake in this message?)

"Thanks" is less formal than "thank you", but it is not inappropriate for a student/teacher, child/parent, ot emplyee/boss relationship, at least in the US.

Your formal expression is fine.