Surplus of atmospheric carbon dioxide causes an increase in the greenhouse effect as carbon dioxide

The correct option is "is opaque to infrared rays".

To understand why this is correct, we need to look at how the greenhouse effect works and how carbon dioxide (${\mathrm{CO}}_2$) interacts with different wavelengths of light.

First, solar radiation from the Sun consists primarily of short-wavelength radiation, including visible light and ultraviolet light. The gases in Earth's atmosphere, including carbon dioxide, are largely transparent to this incoming shortwave solar radiation, allowing it to pass through and heat the Earth's surface.
Once the Earth's surface absorbs this energy, it warms up and re-radiates energy back toward space. However, because the Earth is much cooler than the Sun, it emits energy at much longer wavelengths, specifically in the form of thermal infrared radiation (heat).

Carbon dioxide molecules have vibrational frequencies that match the energy of outgoing thermal infrared radiation. When infrared rays hit a ${\mathrm{CO}}_2$ molecule, the molecule absorbs the energy, causing it to vibrate, and then re-radiates it in all directions, including back toward the Earth's surface.
Because carbon dioxide absorbs and blocks this outgoing infrared radiation from directly escaping into space, it is described as being "opaque to infrared rays."

Therefore, a surplus or increased concentration of atmospheric carbon dioxide traps more of this infrared radiation, leading to an enhanced greenhouse effect and a rise in global temperatures.