The gas which has a rotten egg smell is:

Some gases are odourless but some gases have a distinct smell which also helps in their identification.

Hydrogen peroxide: Hydrogen peroxide has a chemical formula ${\mathrm{H}}_2{\mathrm{O}}_2$. It is colourless when dissolved in water and has a very mild blue hue when it is pure. It is employed as an oxidant, a bleaching agent, as well as an antiseptic, and it has a very strong fragrance. You may get a sense of how hydrogen peroxide smells from its uses. As a result, this is the incorrect response.

Chlorine: With the atomic number 17 and the chemical symbol $\mathrm{Cl}$, chlorine is a chemical element. It belongs to the sixteenth group of the periodic table's halogen family. At room temperature, chlorine is a yellow-green gas that smells strongly of bleach. It is employed as an antibacterial agent in swimming pools and for the purification of drinking water. Therefore, this is not the right response.

Hydrogen sulphide: ${\mathrm{H}}_2\mathrm{S}$ is the chemical formula for hydrogen sulphide. It is a colourless chalcogen hydride gas, which means it contains elements from group 16 and is quite hazardous. It has a smell that is similar to rotting eggs. It is mostly used to make sulphur and sulfuric acid. Therefore, this is the right response.

Carbon dioxide: Its chemical structure is ${\mathrm{CO}}_2$. This colourless, transparent, and odourless gas can make you suffocate if there is too much of it in the air. It plays a significant role in the carbon cycle. As a result, this is the incorrect response.

Thus, the correct option is C.