What piece of evidence supports the theory that volcanic eruptions formed Earth’s early atmosphere.

a. Volcanoes are clustered near the equator, so their gas output spreads all over Earth’s surface.

b. Volcanic eruptions are inversely proportional to local atmospheric pressure.

c. Volcanoes expel a mixture of gases consisting almost entirely of water vapor and oxygen.

d. Volcanoes expel gases with chemical compositions which closely matched the ratios of non-photosynthetic gases in air.