Which of the questions below are acceptable when asking a clerk at a hotel about breakfast?
When is the time for breakfast?
When is the time of breakfast?
What time is breakfast?
My teacher once used the last one. Is he correct?
Which of the questions below are acceptable when asking a clerk at a hotel about breakfast?
When is the time for breakfast?
When is the time of breakfast?
What time is breakfast?
My teacher once used the last one. Is he correct?
Your teacher is correct.
When you use the word when you don't also need to say "the time of" or "the time for". The word when refers to time. That is what it asks about. It literally is a synonym for "what time".
So your teacher's example
What time is breakfast?
is perfectly idiomatic. Also perfectly fine is,
When is breakfast?
Technically,
What is the time for breakfast?
is also grammatically fine, but it sounds stilted and odd, while
What is the time of breakfast?
which is also grammatical, sounds farcical, like someone is making mock of someone very pompous or parodying antique English.