In an agricultural field,which among the following is the highest producer of methane?

Do you observe any soil pollution in your neighbourhood? What efforts will you make for controlling the soil pollution?

Biochemical oxygen demand $(BOD)$ is a measure of organic materials present in water. $A$ $BOD$ value less than $5 \ ppm$ indicates a water sample to be:

Given below are two statements:
Statement $I:$ Classical smog occurs in cool humid climate. It is a reducing mixture of smoke,fog and sulphur dioxide.
Statement $II:$ Photochemical smog has components,ozone,nitric oxide,acrolein,formaldehyde,$PAN$ etc.
In the light of above statements,choose the most appropriate answer from the options given below:

How is chemistry related to the environment? Describe it.

How is biogas produced?