In which of the following industries is animal protein produced as waste?

What is the maximum permissible limit of lead in drinking water in $ppb$?

What do you mean by green chemistry? How will it help decrease environmental pollution?

Which one of the following gases is the major contributor to global warming?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R:$
Assertion $A:$ Polluted water may have a value of $BOD$ of the order of $17 \, ppm$.
Reason $R:$ $BOD$ is a measure of oxygen required to oxidise both the biodegradable and non-biodegradable organic material in water.
In the light of the above statements,choose the most appropriate answer from the options given below.

Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity?