Q: Why will water balloons launched into the air eventually burst?


Read this paragraph and choose the correct option from the provided answers:

Each day, hundreds of weather balloons are launched. Made of a synthetic rubber and carrying a box of instruments, the helium-filled balloon rises up into the sky. As it gains altitude, the atmospheric pressure becomes less and the balloon expands. At some point the balloon bursts due to the expansion, the instruments drop (aided by a parachute) to be retrieved and studied for information about the weather.

 Choices:

- heat

- momentum

- friction

- expansion


A:
expansion