How does the common cold differ from pneumonia?

The correct answer is Option (2) → Pneumonia affects the lungs, while the common cold affects the nose and respiratory passage but not the lungs.

Both diseases are infections of the respiratory system that spread through droplets from an infected person, but they differ in cause and in the part they attack. Pneumonia is caused by bacteria such as Streptococcus pneumoniae and Haemophilus influenzae. It infects the alveoli of the lungs, which fill with fluid. The common cold is caused by rhino viruses. It infects the nose and respiratory passage but not the lungs.

Option (1) The common cold is a nutritional deficiency disease, while pneumonia is a communicable disease. — Incorrect. The common cold is not a deficiency disease. It is an infectious disease caused by rhino viruses, and it is communicable, just like pneumonia.

Option (2) Pneumonia affects the lungs, while the common cold affects the nose and respiratory passage but not the lungs. — Correct. This is the real difference in the site of infection: pneumonia reaches the lungs, while the common cold stays in the nose and respiratory passage.

Option (3) Pneumonia is caused by a virus, while the common cold is caused by the bacterium Haemophilus influenzae. — Incorrect. The causes are given the wrong way round. Pneumonia is bacterial, and Haemophilus influenzae is one of its bacteria. The common cold is viral.

NCERT Extract:
Common Diseases in Humans – “… Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease pneumonia in humans which infects the alveoli (air filled sacs) of the lungs. … Many viruses also cause diseases in human beings. Rhino viruses represent one such group of viruses which cause one of the most infectious human ailments – the common cold. They infect the nose and respiratory passage but not the lungs.”