Answer:
The correct option is: CO₂
Step-by-step explanation:
Greenhouse effect refers to the natural phenomenon by which the Sun's radiation increases the temperature of the Earth's surface.
The incoming Sun's radiation is radiated by the greenhouse gases present in the Earth's atmosphere. A fraction of the radiated energy is then absorbed by the Earth's surface, thus resulting in increase in the temperature.
Thus the green house effect depends upon the amount of green house gases present in the atmosphere.
The green house gases are the radiatively active gases. The main four green house gases are: water vapor (H₂O(g)), carbon dioxide (CO₂), methane (CH₄) and ozone (O₃).
Human activities such as burning of fossil gases and deforestation increases the concentration of CO₂ significantly. Thereby contributing to the greenhouse effect.