Explain why a balloon expands when taken to a higher elevation if the temperature remains constant?

Question

Responses
A The decrease in atmospheric pressure allows the balloon wall to become more elastic.The decrease in atmospheric pressure allows the balloon wall to become more elastic.
B The decrease in atmospheric pressure relative to pressure inside the balloon causes it to expand.The decrease in atmospheric pressure relative to pressure inside the balloon causes it to expand.
C The increase in atmospheric pressure pushes the walls of the balloon outward thus making it larger.The increase in atmospheric pressure pushes the walls of the balloon outward thus making it larger.
D The increase in atmospheric pressure forces the gases to push harder on the balloon increasing its size.

Answer 1

B The decrease in atmospheric pressure relative to pressure inside the balloon causes it to expand.