Excess nitrate in drinking water can cause

The statement "Ozone in the atmosphere is decreased by chlorofluorocarbons $(CF_2Cl_2)$" is:

The concentration of fluoride,lead,nitrate and iron in a water sample from an underground lake was found to be $1000 \ ppb, 40 \ ppb, 100 \ ppm$ and $0.2 \ ppm,$ respectively. This water is unsuitable for drinking due to high concentration of:

In an agricultural field,which among the following is the highest producer of methane?

Fill in the blanks:
$(1)$ Carbon dioxide is found in the ................. layer.
$(2)$ $A$ high concentration of carbon dioxide is responsible for ................. .
$(3)$ ................. gas is used in air conditioners.
$(4)$ Acid rain causes damage to the ................. monument (wonder).

What are pesticides and herbicides? Explain giving examples.