Student or Learner
Hello! Is someone can explain? It seems to me there is a mistake - What's has been your most frightening experience?
Is that possible to use the verb- to be - and - have (has) been- in one question?
You're right. There's a typo. It should say either:
What's been your most frightening experience?
What has been your most frightening experience?
However, your question was wrong. You asked if "to be" and "to have" can be used in the same sentence. They weren't (in your example). "What's been" is a contraction of "What has been". "What's" can be a contraction of "What is", "What has" and even "What does".
Please note my corrections above.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.