What does the idiom 'On cloud nine' mean?

Correct option is B

Option (b) is the correct meaning of the given idiom.
Given Idiom: ‘On cloud nine’: It means to be ecstatically joyful, in a state of intense happiness and delight where one feels elated beyond the ordinary. (Hindi: सातवें आसमान पर , अत्यधिक प्रसन्न/उत्साहित)
Example: When she cleared the exam with top rank, she was on cloud nine for days.
Other related idioms and their meanings:
· Over the moon — extremely happy; delighted.
· Walking on air — feeling light with happiness; elated.
· In seventh heaven — in a state of perfect bliss; extremely happy.
· On top of the world — feeling very pleased and successful.