Based on the Lewis structure for hydrogen and helium, explain why buoyant are filled with helium instead of hydrogen gas, even though gas is cheaper and more buoyant?

Based on the Lewis structures for hydrogen and helium, explain why buoyant balloons are filled with helium instead of hydrogen gas, even though hydrogen gas is cheaper and more buoyant.

H He:

a. Helium's duet makes it stable and inert (unreactive).

b. Helium's duet makes it unstable and chemically reactive.

c. Helium has one more electron than hydrogen, which helps add color to the balloon. 

Based on the Lewis structures for hydrogen and helium, why do buoyant balloons are filled with helium instead of hydrogen gas even though hydrogen gas is cheaper and more buoyant?

(a) Helium's duet makes it stable and inert (unreactive).
(b) Helium's duet makes it unstable and chemically reactive.
(c) Helium has one more electron than hydrogen, which helps add color to the balloon.

A balloon filled with helium gas is found to take 4.7 hours to deflate to 55% of its original volume. How long (in hr) will it take for an identical balloon filled with the same volume of hydrogen gas (instead of helium) to decrease its volume by 55%?

_______hr

A explanation would be helpful