Without green house effect, the average temperature of earth’s surface would have been —
(a) -18°C
(b) 33°C
(c) 0°C
(d) 15°C

(a) -18°C

Reason — In the absence of green house gases from the atmosphere, entire heat energy radiated from the earth’s surface and objects on it, would escape out into space and then average temperature on earth would be -18°C instead of 15.5°C .