Thom reads an article on the internet that that claims some lakes on Saturn are contain frozen methane. He reads that there is methane on Neptune, too. Which sentence best describes data that would suggest methane is frozen on Neptune?

a
Neptune's atmosphere has more methane than Saturn's.
b
Neptune's mass is less than Saturn's.
c
Neptune's surface temperature is colder than Saturn's.
d
Neptune's distance from the Sun is greater than Saturn's.