GK (General Science)

Wisdom teeth are the third and final set of molars that most people get in their late teens or early twenties (ages 17-25). They are called 'wisdom teeth' because they appear at a more mature age, when people are supposedly wiser than childhood. These teeth often cause problems because there is not enough room in the jaw for them to emerge properly, leading to impaction that may require surgical removal.

Sharks have skeletons made entirely of cartilage rather than bone, which makes them lighter and more flexible than bony fish. This type of skeleton is characteristic of cartilaginous fish (Chondrichthyes), a group that also includes rays and skates. Cartilage is a firm but flexible connective tissue that allows sharks to swim efficiently and maneuver quickly through water. Their cartilage skeleton also heals more slowly than bone when injured.

Myology is the branch of anatomy that specifically studies the muscular system, including muscle structure, function, development, and diseases. This field examines the approximately 600 muscles in the human body, how they contract to produce movement, and their role in maintaining posture and generating heat. In contrast, osteology studies bones, odontology studies teeth, and onychology studies nails - none of which are related to myology.

Hemoglobin is a complex protein (specifically a globular protein) found in red blood cells that contains iron and is responsible for carrying oxygen from the lungs to tissues throughout the body. Each hemoglobin molecule can carry four oxygen molecules. It is not a mineral (though it contains iron), not plasma (the liquid portion of blood), and not simply an 'organic substance' - it is specifically a structured protein with a precise molecular composition essential for respiration.

A scramjet carries fuel (usually hydrogen) but scoops oxygen from the atmosphere instead of carrying it onboard, making it more efficient than rockets which must carry both. Option C states scramjets carry no fuel at all, which is false - they eliminate carrying oxygen, not fuel. Since the question asks which statement is NOT true, C is the correct choice.

Richard J. Roberts and Phillip A. Sharp discovered split genes (genes containing introns) in 1977 through their research on adenovirus. They showed that genes could be discontinuous, with non-coding regions (introns) removed during RNA processing. This breakthrough earned them the 1993 Nobel Prize in Physiology or Medicine.

Acetic acid (found in vinegar) was known to ancient civilizations including Babylonians (around 3000 BCE), who used it in food preservation. It was the first acid systematically documented and used in practical applications. Amino acids were discovered much later (aspartic acid in 1868), and alginic acid was discovered in 1881.

The moon illusion is primarily caused by atmospheric refraction - light bends as it passes through different density layers of Earth's atmosphere, especially near the horizon. This refraction makes celestial objects appear larger when low in the sky. Total internal reflection, scattering, and diffraction don't cause this effect.

Leukemia is a cancer of blood-forming tissues, primarily the bone marrow and lymphatic system. It involves the overproduction of abnormal white blood cells, which crowd out healthy blood cells and cannot function properly. While it can spread to other organs, it originates in and primarily affects the blood and blood-producing tissues.

Sound travels fastest through solids because their molecules are tightly packed and rigidly bonded, allowing efficient energy transfer through molecular vibrations. Steel is denser than water, and air is much less dense, while vacuum doesn't transmit sound at all. The speed of sound in steel (5000 m/s) far exceeds that in water (1500 m/s) or air (~340 m/s).

The hyoid bone is unique in the human body because it's the only bone that doesn't articulate (form a joint) with any other bone. It floats in the neck, suspended by ligaments and muscles, and supports the tongue and other structures. All other bones listed (femur, tibia, ulna) form joints with other bones.

Cardiac massage (chest compressions) is the immediate priority in cardiac arrest to maintain blood circulation to vital organs, especially the brain. While mouth-to-mouth respiration is part of CPR, compressions come first and are most critical. Medication and artificial oxygen are secondary interventions provided by medical professionals.

Digestive enzymes (like amylase, protease, lipase) break down food molecules into smaller absorbable units during digestion. They catalyze specific reactions - carbohydrates to sugars, proteins to amino acids, fats to fatty acids. While enzymes play roles in many body processes, the digestive system is their primary domain.

Pasteurization kills harmful microorganisms (bacteria, pathogens) by heating milk to specific temperatures (usually 63°C for 30 minutes or 72°C for 15 seconds). This process was developed by Louis Pasteur to make milk safe for consumption. It doesn't significantly enhance taste, increase nutritional value, or detect adulteration - its primary purpose is safety.

Red blood cells (erythrocytes) have a lifespan of approximately 120 days in the human body. After this period, they are removed from circulation by the spleen and liver, and their components are recycled. The 120-day lifespan is a well-established fact in human physiology.

R.T.H. Laënnec invented the stethoscope in 1816. He was a French physician who created this diagnostic tool to listen to heart and lung sounds without placing his ear directly against the patient's body. The stethoscope revolutionized physical examination and remains a fundamental medical instrument today.

High-Density Lipoproteins (HDLs) are called 'good' cholesterol because they transport cholesterol from tissues back to the liver for excretion, which helps prevent plaque buildup in arteries. HDL acts as a scavenger, removing excess cholesterol. LDL and VLDL are considered 'bad' cholesterol as they deposit cholesterol in arterial walls, contributing to atherosclerosis.

Polarized glass is used in sunglasses to reduce glare from reflective surfaces, in camera filters to manage reflections and enhance contrast, but standard mirrors do not use polarized glass. Mirrors work by specular reflection using metallic coatings (silver, aluminum) on glass, which doesn't require polarization. While polarizing mirrors exist for specialized applications, standard mirrors are not polarized.

For AC power transmission, the RMS voltage in India is 220V. The peak voltage (maximum instantaneous value) is √2 times the RMS value, so peak = 220 × √2 = 220 × 1.414 = 311V approximately. This peak value represents the maximum voltage reached during each cycle of the alternating current waveform. 220V is the RMS (root mean square) voltage, which is the effective DC equivalent.

Ptyalin (also known as salivary amylase) is an enzyme present in saliva, which is produced in the mouth by salivary glands. It begins the digestion of starch into simpler sugars like maltose. The enzyme works optimally in the slightly acidic to neutral pH of the mouth (pH 6.7-7.0). No ptyalin is present in the stomach, pancreas, or liver.

The ossicles (malleus, incus, and stapes) are the three smallest bones in the human body, located in the middle ear. The stapes is the smallest of all, measuring approximately 3mm × 2.5mm. These tiny bones transmit sound vibrations from the eardrum to the inner ear. The tibia, skull bones, and kneecap (patella) are all significantly larger.