Jupiters atmosphere is mostly made of
a. helium
b. methane
c. ammonia
d. hydrogen

Jupiter's atmosphere is composed predominantly of hydrogen and helium, but if you have to select any one option then we can look at the percentage of existence of these elements that would be
90 percent hydrogen.
remaining 10 percent is helium 
so choose Hydrogen.

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

The correct answer is "atomic weight".