Answer the following briefly .-

(i) Mention two functions of the World Health Organization.

(ii) Explain the following terms :

(1) Immunity

(2) Acid rain.

(iii) Define the term Antibiotic. Give an example of an antibiotic. 

(i) Two functions of WHO are:

1. Research - To support and promote projects for research on diseases.
2. Pharmaceutical standards - To set pharmaceutical standards for vital medicines, thus regulating the quality and the quantity of the dose.

(ii)
(1) Immunity is the resistance to the onset of a disease, after being infected by harmful germs.

(2) Atmospheric oxygen oxidises sulphur dioxide, nitrous oxide and nitric oxide to sulphur trioxide, nitric oxide and nitrogen dioxide respectively, which dissolve in rainwater to form sulphuric acid, nitrous acid and nitric acid respectively. The acidified water thus formed falls on the Earth's surface as acid rain.

(iii) Antibiotic is a chemical substance manufactured by various microorganisms like bacteria and fungi, which inhibits or ceases the growth of other microorganisms.For e.g. Penicillin, streptomycin, chloromycin, aureomycin, ampicillin.