What is the intensity of sound in normal conversation?

Assertion $(A)$: Pollution is always caused by human activities.
Reason $(R)$: Pollution is not different from contamination.

What is hybrid vehicle technology? Explain its advantages with a suitable example.

Define/Explain: Smog.

What is used to remove particulate matter from industrial exhaust?

In the treatment of wastewater,scientists at the Arcata Marsh (a project associated with Humboldt State University) developed a series of six connected marshes over how much area to remove heavy metals and other pollutants?