B. Argon's vibrational energy is not excited by infrared radiation.
Explanation:
The property of carbon dioxide to get excited by infrared electromagnetic radiation is what qualifies it as a greenhouse gas. When infrared from the earth's surface is reflecting back to space, some of the radiation is absorbed and remitted by the carbon-dioxide molecules in the atmosphere. This causes a phenomenon called greenhouse effect that causes the atmosphere to be relatively warmer. The more the carbon dioxide molecules the more the greenhouse effect.