Define contaminant. Give an example.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

Methyl isocyanate $\left({\mathrm{CH}}_3\mathrm{NCO}\right)$ is a contaminant. 

Subsoil and groundwater act as source for pesticides used in agriculture.