Can someone help me with this question,

Which compound has the largest percent by mass of nitrogen?
A) NO2
B) N2O3
C) N2O
D) NO

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.