Most hazardous metal pollutant of automobile exhaust is

Which of the following practices will not come under green chemistry?
$1$. Using soaps made of vegetable oils instead of synthetic detergents,whenever possible.
$2$. Using $H_2O$ for bleaching purposes instead of chlorine-based bleaching agents.
$3$. Using liquefied $CO_2$ for dry cleaning clothes and laundry.
$4$. Using plastic cans for neatly storing substances.

Depletion of ozone layer is caused by

Which one of the following is mainly responsible for the depletion of the ozone layer?

The higher concentration of which gas in air can cause stiffness of flower buds?

Which of the following is not an air pollutant?