Impurities of water are

What is the $BOD$ limit prescribed by the $CPCB$ for natural water bodies into which municipal waste is discharged?

According to the $..........$ norms,the implementation of $.......$ vehicles was enforced across the country from $1^{st}$ April $2017$.

Particulate matter with a diameter of $2.5$ micrometres or less and a sound level of $150$ $dB$ or more causes the greatest harm to human health.

The pesticide used in the foundations of buildings for preventing termite attack is:

$A$ - Micro-organisms involved in the biodegradation of organic matter in the receiving water body consume a lot of oxygen,and as a result,there is a sharp decline in dissolved oxygen in the stream from the point of sewage discharge.
$R$ - $BOD$ decreases when the dissolved oxygen amount decreases in water.