D IS THE ANSWER TO YOUR QUESTION
D. An animal decaying after it dies seem to be the right answer hopefully.
You just need to convert it into moles per Liter (mol/L).
0.0815mol / 0.550L = 0.148mol/L
125 mile *1gallon/35 mi = 135/35 = (27/7) gallon gasoline
27/7 gallon * 1 L/0.264 gallon = 14.6 L gasoline
14.6 L gasoline * 2.5kg CO2/1L gasoline= 36.5 kg CO2
36.5 kg CO2 * 1lb/0.454 kg = 80.4 lb
Answer: 80.4 lb CO2
More sleep and longer days or nights