GK (Science)

Benzoic acid and its sodium salt (sodium benzoate) are commonly used as food preservatives because they effectively inhibit the growth of bacteria, yeast, and molds in acidic foods. Acetic acid (vinegar) is used but less commonly as a preservative.

Fumigation is the process of using chemical gases (fumes) to destroy harmful bacteria, pests, or insects in enclosed spaces. The chemical fumes penetrate and kill the organisms. Fermentation is a biological process, culturing grows bacteria, and 'heat killing' is not a standard term.

Compost is considered a balanced fertilizer because it contains a mix of essential nutrients (nitrogen, phosphorus, potassium) and organic matter that improves soil structure. Urea, super phosphate, and ammonium sulfate are single-nutrient fertilizers, lacking the complete balance plants need.

Tea requires large amounts of rainfall (2000-2500mm annually) but needs well-drained soil and cannot tolerate standing water. Rice requires standing water, groundnut needs less water, and jute needs water but can tolerate some waterlogging.

Plants are grown along river banks primarily to reduce soil erosion and silting. Their root systems hold the soil in place, preventing it from being washed away by water flow. They don't primarily control pollution, provide shade, or prevent floods.

Red soil gets its color from the presence of iron oxide compounds, particularly hematite and limonite. These iron compounds give the soil its characteristic reddish or reddish-brown appearance. The color indicates iron content, not potash, nitrogen, or humus.

Carbohydrates are the primary ready source of energy for athletes because they are quickly broken down into glucose and used for immediate energy. Carbs replenish glycogen stores in muscles. Fats and proteins provide sustained energy but are slower to metabolize.

Rabi crops are winter crops sown in October-November and harvested in spring. March-April is the correct harvest period as the crops mature during winter and are ready for collection before the onset of summer. June-July and August-September are kharif crop seasons, while October-November is when rabi crops are sown, not harvested.

The gestation period of cows is approximately 285 days, making 280 days the closest correct option among the choices. Cows carry their calves for about 9 months, similar to humans. 365 days would be too long (a full year), while 300 days is slightly longer than the actual period, and 150 days (5 months) is far too short for cattle.

Eucalyptus is indeed one of the fastest growing trees among the options, capable of growing several meters per year under favorable conditions. Teak is a slow-growing hardwood tree that takes decades to mature. Banyan trees grow slowly and spread widely over time, while coconut palms have moderate growth rates but are not considered exceptionally fast-growing compared to eucalyptus.

Palak (spinach) is indeed rich in iron, which is essential for hemoglobin formation and preventing anemia. While palak also contains vitamin A and some carotene, iron is its most notable nutrient. Vitamin D is not found in palak. Leafy greens like spinach are specifically recommended for iron deficiency.

Marek's disease is a highly contagious viral disease that specifically affects poultry, particularly chickens. It causes tumors in nerves and organs. The disease does not affect cows, goats, sheep, or elephants - these are different species with different disease susceptibilities. It's a major concern in poultry farming worldwide.

Groundnut (peanut) is indeed valued for both its oil content (approximately 45-50% oil) and its high protein content (approximately 25-30%). It serves dual purposes as both an oilseed crop and a protein source. Coconut is primarily valued for oil, areca nut is not typically used for oil extraction, and hazelnut is not commonly grown as an oilseed crop.

Starch and sugars are both classified chemically as carbohydrates, which are one of the three main macronutrients along with proteins and fats. Starch is a complex carbohydrate (polysaccharide) while sugars are simple carbohydrates (monosaccharides and disaccharides). Antibodies are proteins, not related to starch and sugars.

Vitamin K - Scurvy is indeed incorrectly matched. Scurvy is caused by Vitamin C deficiency, not Vitamin K deficiency. Vitamin K is associated with blood clotting, and its deficiency causes bleeding disorders. The other options are correctly matched: Vitamin D with bone deformities (rickets), Vitamin B with beriberi, and Vitamin A with night blindness.

Carbohydrates in the human body are stored as glycogen, primarily in the liver and muscles. Liver glycogen maintains blood sugar levels, while muscle glycogen provides energy for muscle contraction. Carbohydrates are not stored in kidneys, and storing them in only one location (either liver or muscles alone) would not meet the body's energy needs.

Vitamin C is well-known for increasing resistance to infection by supporting immune system function, promoting white blood cell activity, and acting as an antioxidant. It helps protect against colds, flu, and other infections. Vitamins D, B, and A have important functions but are not specifically known for enhancing infection resistance.

Vitamin C is chemically known as ascorbic acid, which is its scientific name. Citric acid is found in citrus fruits but is not vitamin C. Lactic acid is produced in muscles during anaerobic respiration. Folic acid is actually Vitamin B9. The chemical structure of vitamin C is ascorbic acid.

Green leafy vegetables like spinach, fenugreek, and amaranth leaves contain significant iron, though pulses (especially with vitamin C) and eggs are also excellent sources. The key is iron bioavailability - plant-based iron is enhanced when consumed with vitamin C-rich foods.

Niacin (vitamin B3) deficiency causes pellagra, characterized by the 3 Ds: dermatitis, diarrhea, and dementia. Marasmus and kwashiorkor are protein-energy malnutrition disorders, while goitre results from iodine deficiency.

Vitamin A deficiency leads to night blindness initially, which can progress to complete blindness (xerophthalmia) if untreated. Beriberi is caused by thiamine deficiency, rickets by vitamin D deficiency, and typhoid is a bacterial infection, not a deficiency.

Diabetes mellitus involves problems with insulin - either insufficient production (Type 1) or insulin resistance (Type 2), not a deficiency of glucose or vitamins A or C. Insulin is the hormone that regulates blood glucose levels.