Aedes aegypti transmits dengue virus.

Rainfall is measured using a rain gauge, a meteorological instrument designed to collect and measure precipitation. It typically consists of a funnel that directs rainwater into a measuring cylinder. The amount of rainfall is recorded in millimeters, representing the depth of water that would accumulate on a flat surface. Accurate rainfall data is essential for agriculture, flood prediction, and weather forecasting. A hydrometer measures liquid density, not rainfall. “Rain meter” and “hydroscope” are not standard instruments. Thus, rain gauge is the correct answer. It is widely used by meteorological departments worldwide.

Pancreatic enzymes are released into the duodenum where they aid digestion of carbohydrates, proteins, and fats.

Sulphur dioxide causes corrosion by forming sulphuric acid in presence of moisture, damaging iron and steel structures over time. It accelerates rusting and weakens metal integrity, especially in polluted industrial environments.

Villi are small, finger-like projections found in the inner lining of the small intestine. Their main function is to increase the surface area for absorption of nutrients. Each villus contains blood vessels and lymphatic vessels (lacteals) that help absorb digested nutrients such as glucose, amino acids, and fatty acids. This adaptation makes nutrient absorption highly efficient. The large intestine mainly absorbs water and salts and does not have villi. The stomach is involved in digestion but not absorption at this level. The liver processes nutrients but does not contain villi. Thus, the small intestine is the correct answer. This concept highlights the importance of structural adaptations in biological systems to enhance function. Understanding villi is crucial in topics like digestion, absorption, and diseases such as celiac disease, where villi are damaged.