What is the biggest difference between Earth's modern atmosphere and the atmosphere of Venus?

A.
Earth's atmosphere is primarily nitrogen and oxygen; Venus's atmosphere is primarily carbon dioxide and nitrogen.
B.
Earth's atmosphere is primarily nitrogen and oxygen; Venus's atmosphere is primarily carbon dioxide and methane.
C.
Earth's atmosphere is primarily oxygen and carbon dioxide; Venus's atmosphere is primarily carbon dioxide and nitrogen.
D.
Earth's atmosphere is primarily oxygen and carbon dioxide; Venus's atmosphere is primarily carbon dioxide and methane.