Correct Answer:
C. To be extremely happy
This question requires understanding the meaning of the idiom “On cloud nine.” Idioms have figurative meanings that differ from the literal interpretation of their words.
- To be extremely happy is the correct answer. The idiom 'on cloud nine' signifies a state of intense joy, euphoria, or bliss.
- To be lost in thoughts (A) describes being preoccupied or distracted, not necessarily happy.
- To travel in space (B) is a literal interpretation of 'cloud nine', which is incorrect for an idiom.
- To be far from home (D) describes a physical location, which is unrelated to the emotional state conveyed by the idiom.
Hence, 'to be extremely happy' accurately defines the idiom 'on cloud nine'.