Bihar Police SI Science — practice by topic

Answer: C. Cicada, Froghopper and Pond skater are all INSECTS. (1) Cicada (Hemiptera: Cicadidae) is a true bug famous for the loud songs of males. (2) Froghopper (Hemiptera: Cercopidae) is the insect whose nymphs produce the protective 'spit' (cuckoo-spit) on plants. (3) Pond skater (Hemiptera: Gerridae) is the aquatic insect that walks on the water surface thanks to hydrophobic legs and surface tension. All three are members of the order Hemiptera (true bugs). None are birds, fish or reptiles. Source: syllabus Biology Ch 4 (Animal Kingdom) and standard entomology references.

Answer: A. Nitric oxide (NO) is the body's natural vasodilator. Nitric oxide is a free-radical signalling molecule produced in the body by endothelial cells lining blood vessels. It diffuses to the smooth muscle around vessels and triggers relaxation, causing vessels to dilate and blood flow to increase. The discovery of NO as a signalling molecule won the 1998 Nobel Prize in Physiology or Medicine (Furchgott, Ignarro, Murad). Drugs like nitroglycerin work by releasing NO to relieve angina. **Distractors fail:** (B) Nitrous oxide N2O is laughing gas, an anaesthetic, not a natural vasodilator. (C) Nitrogen dioxide NO2 is a toxic air pollutant. (D) Nitrogen pentoxide N2O5 is an unstable industrial intermediate, not biologically synthesised. Source: syllabus Biology / Nobel Prize 1998 citation.

Answer: D. Membrane bioreactors (MBRs) are used in WASTEWATER TREATMENT. MBR combines a conventional biological treatment process (activated sludge) with a membrane separation step that replaces the secondary clarifier. The membrane (microfiltration or ultrafiltration) physically separates treated water from biomass, producing high-quality effluent suitable for reuse. MBRs are widely used in municipal sewage treatment plants and industrial wastewater treatment. India's Central Pollution Control Board recognises MBR as an advanced sewage treatment technology, particularly in space-constrained urban locations. **Distractors fail:** (A) ART uses different reproductive biology equipment. (B) Drug delivery uses microspheres and liposomes, not bioreactor membranes. (C) Vaccine production uses bioreactors but not specifically membrane bioreactors as the defining technology. Source: CPCB sewage treatment guidelines / Jal Shakti Ministry technology reports.