Question

which gases contribute to the greenhouse effect?
nitrogen and helium
carbon dioxide and methane
carbon dioxide and helium
nitrogen and methane

Explanation:

Greenhouse gases trap heat in the atmosphere. Carbon dioxide ($\ce{CO_2}$) is released by fossil fuel burning, deforestation, etc. Methane ($\ce{CH_4}$) comes from sources like livestock, rice paddies, and natural gas systems. Nitrogen and helium are not greenhouse gases. So carbon dioxide and methane contribute to the greenhouse effect.

Answer:

B. carbon dioxide and methane (assuming the options are labeled as A: nitrogen and helium, B: carbon dioxide and methane, C: carbon dioxide and helium, D: nitrogen and methane)