Black foot disease is caused by the toxicity of which of the following?

Spraying $DDT$ on crops causes pollution of .......

$A$: Nitrate and phosphate discharge in a water body causes eutrophication.
$R$: This increases the inorganic content in the water body and hence the growth of algal blooms.

$SO_{2}$ pollution is indicated by

Decibel $(dB)$ is a standard abbreviation used for the quantitative expression of

Which of the following statements is correct?