The structure of DNA was discovered by: MCQ with Answer and Explanation

Explanation:
Kala-azar (visceral leishmaniasis) is caused by the protozoan Leishmania donovani, transmitted by sandfly bite. Tetanus is bacterial (Clostridium tetani), tuberculosis bacterial (Mycobacterium tuberculosis), measles viral. Protozoan diseases include malaria, amoebiasis, sleeping sickness, giardiasis. Kala-azar causes fever, weight loss, splenomegaly, and is endemic in parts of India.

Explanation:
A food web is a complex network of interconnected food chains showing multiple feeding relationships in an ecosystem. Decomposers (bacteria and fungi) break down dead organic matter, returning essential nutrients to the soil for producers. Due to energy loss at each transfer (10% law), the total biomass generally decreases at higher trophic levels, forming an upright pyramid. All statements are correct.

Explanation:
Motilin is a peptide hormone secreted by the Mo cells (or M cells) in the crypts of the duodenum and jejunum. Its secretion occurs in cycles during the fasting (interdigestive) state. Its primary function is to stimulate gastric motility and emptying, and to initiate and regulate the Migrating Motor Complex (MMC). The MMC is a pattern of electromechanical activity observed in the gastrointestinal tract during fasting, characterized by waves of contraction that sweep undigested material, bacteria, and sloughed cells from the stomach and small intestine towards the colon, acting as a 'housekeeper'.