Which of the following vitamins is essential for blood clotting? MCQ with Answer and Explanation

Explanation:
Alveoli are tiny air sacs surrounded by capillaries where gas exchange (O₂ and CO₂) occurs. Nephrons are kidney units, neurons nerve cells, villi intestinal projections. The lungs contain millions of alveoli to maximize surface area.

Explanation:
The Widal test is a serological agglutination test used to diagnose enteric (typhoid) fever, caused by Salmonella enterica serotype Typhi. It detects the presence of specific antibodies (O and H antigens) in the patient's serum against the O (somatic) and H (flagellar) antigens of the Salmonella typhi bacteria. A significant rise in antibody titer indicates an active or recent infection. It is not used for TB (Mantoux test), malaria (blood smear), or dengue (NS1/IgM).

Explanation:
Rabies is a viral zoonotic disease caused by the rabies virus, transmitted through the saliva of infected animals (dogs, bats, raccoons) via bites or scratches. It affects the central nervous system and is almost always fatal once symptoms appear. Post-exposure prophylaxis (wound cleaning, rabies immunoglobulin, and vaccine) is effective if given promptly.