Pollution is the will have the greatest effect on human health

troposphere
stratosphere
mesosphere
thermosphere

Troposphere

Explanation:

Troposphere is the lowest layer of the earth atmosphere. Most of the clouds are found in this layer. It can influence the weather condition in a region. It can be affected by the pollution due to the abundance of toxic poisonous gases in the atmosphere. This layer of atmosphere affects the human health. The toxic gases may cause respiratory diseases like asthma, bronchitus and others.

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.