GK (Science)

Stainless steel is an iron-based alloy that contains chromium as its essential element, with nickel and manganese as common additional components. Chromium (minimum 10.5%) provides corrosion resistance by forming a protective oxide layer on the surface. Nickel enhances corrosion resistance and mechanical properties, while manganese improves hot working properties and contributes to the alloy's strength and toughness.

Isotopes are atoms of the same element with identical proton counts but different neutron counts. This gives them the same chemical properties but different atomic masses. Isobars have same mass number, compounds are combinations of elements, and allotropes are different structural forms of the same element.

Hydrogen sulphide (H2S) reacts with copper in brass to form black copper sulphide, causing discoloration. Oxygen and nitrogen don't react noticeably with brass under normal conditions. Carbon dioxide doesn't significantly tarnish brass compared to H2S's strong reaction with copper.

Mercury is the only metal that is liquid at room temperature (standard conditions). Hydrogen and chlorine are non-metal gases, and water is a liquid compound but not a metal. This is a fundamental property of mercury.

The question asks for INCREASING order (least to most). Argon (0.93%) is least abundant, then oxygen (21%), then nitrogen (~78%). So argon < oxygen < nitrogen is correct. Option B states 'argon, oxygen and nitrogen' which matches this increasing order.

Diamond and graphite are both pure carbon allotropes with identical atomic weights (12 for carbon-12). They differ in crystal structure (diamond: tetrahedral, graphite: layered hexagonal), density (diamond: 3.51 g/cm³, graphite: 2.26 g/cm³), and electrical conductivity (diamond: insulator, graphite: conductor).

Endocrine glands secrete hormones directly into the bloodstream to regulate body functions. Plasma cells produce antibodies, salivary glands produce saliva (exocrine), and prostate glands produce fluid for semen (exocrine). Only endocrine glands are primarily defined by hormone secretion.

Hybridization is the mating of genetically different lines to combine desirable traits from both parents. Inbreeding is mating of closely related individuals, selection is choosing preferred traits, and outbreeding is mating of unrelated individuals (but not necessarily distinct lines). Hybridization specifically targets combining different genetic lines.

  Urea is nitrogenous fertilisers which is not very effective in acidic soils.

Carbon monoxide is extremely toxic because it binds to hemoglobin 240 times more strongly than oxygen, preventing oxygen transport and causing asphyxiation. CO2 and N2 are asphyxiants at high concentrations but less immediately toxic, while hydrogen is flammable but not typically described as 'toxic' in the same way as CO.

Insulin regulates blood glucose by promoting cellular glucose uptake and storage. Iodine is for thyroid function, hemoglobin carries oxygen, and glycogen is stored glucose (not a regulator). Insulin lowers blood sugar, while glucagon raises it - together they maintain glucose homeostasis.

Asthma primarily affects the respiratory tract, causing bronchial tube inflammation, constriction, and mucus production that makes breathing difficult. While lungs contain the affected airways, 'respiratory tract' more precisely describes the system impacted. Asthma doesn't directly affect heart or liver function.

Diphtheria is a communicable disease caused by the bacterium Corynebacterium diphtheriae, which spreads through respiratory droplets or direct contact. Cancer, Diabetes, and Rheumatism are non-communicable diseases - they cannot be transmitted from person to person.

Carrots are one of the richest sources of vitamin A (as beta-carotene), which the body converts to retinol. Jaggery provides mainly iron and sucrose, Ragi is rich in calcium and iron, and Gooseberries (amla) are excellent for vitamin C, not vitamin A.

Pearls are formed inside oysters (marine bivalve mollusks) as a defense mechanism against irritants like parasites or debris. When an irritant enters the shell, the oyster secretes nacre (mother-of-pearl) around it, gradually forming a pearl.

Human males have XY sex chromosomes, while females have XX. The Y chromosome carries the SRY gene that triggers male development. YY is not viable in humans, XO causes Turner syndrome, and XX is the female karyotype.

Anemia is directly caused by nutritional deficiencies, particularly iron, folate, or vitamin B12 deficiency. While Scurvy results from vitamin C deficiency and Flurosis from excess fluoride, Diabetes is a metabolic disorder, not primarily a nutritional deficiency disease.

Malaria is caused by protozoan parasites of the Plasmodium genus, transmitted by Anopheles mosquitoes. Typhoid is bacterial, Night blindness is from vitamin A deficiency, and Ringworm is a fungal infection - none are protozoan.

Meningitis specifically refers to inflammation of the meninges, the protective membranes covering the brain and spinal cord. The prefix "mening-" relates to these membranes, while "-itis" indicates inflammation. Sinusitis affects sinuses, Hepatitis affects the liver, and Tonsillitis affects tonsils.

Typhoid fever is caused by Salmonella typhi, a bacterium transmitted through contaminated food and water. Rabies is viral, Night blindness is from vitamin A deficiency, and Ringworm is fungal - only Typhoid is bacterial among these options.

Vitamin C significantly enhances non-heme iron absorption by reducing iron to its ferrous (Fe²⁺) form and forming soluble complexes that prevent precipitation. This is why iron-rich foods are best consumed with vitamin C sources like citrus fruits. Vitamins A, B, and D don't have this specific effect on iron absorption.

German measles (Rubella) during pregnancy can cause congenital rubella syndrome, leading to severe birth defects including heart problems, deafness, and intellectual disabilities. This risk is highest in the first trimester. Chickenpox, Smallpox, and Measles also pose risks but Rubella is most strongly associated with the recommendation for pregnancy termination.