The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs

Answer: (d) the infrared part of the solar radiation

CO₂ absorbs infrared (heat) radiation — mostly the infrared given off by the warm Earth — and sends some back down.

The idea

Sunlight comes in mostly as short-wave light and passes through the air easily. The warmed Earth sends heat back as long-wave infrared. Carbon dioxide lets the sunlight in but absorbs this outgoing infrared and sends part of it back down. More carbon dioxide means more heat held back.

Sunlight passes through the air → Ground warms up → Ground gives off infrared → CO₂ absorbs it → Part is sent back down → Lower air warms

Why the others are wrong

(b) Ozone absorbs UV; CO₂ does not.

(c) CO₂ lets most sunlight through.

The trap

Strictly, CO₂ traps outgoing infrared from the Earth, not “solar” infrared — but (d) is the only option about infrared.

Elimination technique

Option (c) says CO₂ absorbs “all the solar radiations”. Absolute words usually mark the wrong option in Environment PYQs.

Also know

Without any greenhouse effect the Earth’s average temperature would be about −18°C instead of about 15°C, so the natural effect is necessary for life; the problem is the added part. Carbon dioxide in the air has risen from about 280 parts per million before industry to more than 420 now. The longest record is from Mauna Loa, Hawaii (the Keeling curve).