The sentence is in the present perfect continuous tense, which requires the verb in the "-ing" form to indicate an ongoing action.
The correct sentence should be:
"He has been listening to music for the past hour."
Thus, the correct answer is (A) "listening."
Arun’s present age in years is 40% of Barun’s. In another few years, Arun’s age will be half of Barun’s. By what percentage will Barun’s age increase during this period?