Genetic disorders result from errors in the DNA of our body cells. Hormonal disorders (for e.g. excessive growth, appearance of facial hair in females, etc) are the results of imbalanced secretion of hormones produced within the body. Similarly, if any body organ malfunctions, i.e. it does not function in proper order, then it is an internal cause. But if there is malnutrition, then the cause is purely external and not within our body. We should remember that cause may be external or internal, but the effect is seen on the general health of our body.

 The AIDS virus does not spread through handshake. 

Health refers to physical, mental and social well-being. Thus, absence of any tension, anxiety (mental factors) and social problems contribute to health. But absence of work is not a factor that can make us healthy. Hence, (2) is the correct answer.

Common cold, pneumonia and tuberculosis are airborne diseases, i.e. they spread through air because their causative agents, i.e. virus and bacteria, are present in the air. On the contrary, malaria is not airborne because it is caused by Plasmodium, which spreads through the bite of female anopheles mosquitoes and is not present in the air. Thus, (4) is the correct answer.

Diarrhoea is an infection of stomach (gastro) and intestine in which the person suffers from water loss and loose stools. Hence, it is a gastrointestinal disorder (as is clear from its name).

Health is a state of being well enough to function well physically, mentally and socially. An individual can be in poor health without having any identifiable disease.

SARS is a respiratory disease caused by a virus. Symptoms usually occur about 2 to 10 days after coming in contact with the virus.

Edward Jenner created the vaccine for smallpox two centuries ago.

An adulterant of arhar (tuhar) dal is metanil yellow.

A common adulterant found in turmeric powder is lead chromate. It can cause anemia, abortion, paralysis and brain damage.

Dropsy is a disease caused due to adulteration in mustard oil. It is the abnormal accumulation of body fluids in arms and legs.

 Rickets is a condition that affects bone development in children.

Pellagra is a vitamin deficiency disease caused by a chronic lack of niacin (vitamin B₃).