$BOD$ values (in $ppm$) for clean water $(A)$ and polluted water $(B)$ are expected respectively:

Arrange the following greenhouse gases in the correct decreasing order of their contribution to global warming.

The acceptable level of carbon monoxide gas $(CO)$ in the atmosphere in $ppm$ level is

How is electricity produced in a thermal power station?

$A.$ Ammonium salts produce haze in the atmosphere.
$B.$ Ozone is produced when atmospheric oxygen reacts with chlorine radicals.
$C.$ Polychlorinated biphenyls act as cleansing solvents.
$D.$ 'Blue baby' syndrome occurs due to the presence of excess nitrate ions in water.
Choose the correct answer from the options given below:

The chlorine free radical reacts with ozone to form a ..... free radical.