HELLPPP I asked this multiple times can sum1 please help:((( Which of the following is the MOST common source of indoor air pollutants in less-developed countries?

A. poorly ventilated cooking fires
B. carbon monoxide from vehicles
C. cleaning solvents
D. air-conditioning units

The greenhouse effect a. something that has occurred for millions of years b. an unnatural phenomenon caused by humans that maintains earths temperature range. c. the results of the differences in the angle of the suns rays d. an unnatural phenomenon that causes heat energy to be radiated back into the atmosphere