I know you all are smart enough to guess this, plus there is only 3 answers! Go for it!

You're sitting on a bus. The kid next to you has a helium-filled balloon and it ends up against the ceiling, just about in the center of the bus. The driver suddenly hits the gas pedal and the bus lurches forward, throwing you back into your seat. What does the balloon do?

a. It moves backwards.
b. It moves forward.
c. It stays where it is.