The two gases making highest relative contribution to the greenhouse gases are

Step-by-step solution

The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of earth's surface and atmosphere. Clouds and gases reflect about one-fourth of the incoming solar radiation and absorb some of it but almost half of incoming solar radiation falls on earth's surface heating it, while a small proportion is reflected back. Earth's surface re-emits heat in the form of infrared radiation but part of this does not escape into space as atmospheric gases (eg CO ₂, CH ₄ etc) absorb a major fraction o