General Science

Thomas Alva Edison invented the first practical electric light bulb in 1879. While there were earlier versions by other inventors like Joseph Swan, Edison's design was the first commercially successful incandescent lamp with a long-lasting carbon filament. The other options are incorrect: Dr. C.V. Raman discovered the Raman effect, Alfred Nobel founded the Nobel Prize and invented dynamite, and Alexander Fleming discovered penicillin.

Dialysis is a medical treatment that artificially removes waste products and excess fluid from the blood when the kidneys are not functioning properly. The kidneys normally filter blood, but when they fail due to chronic kidney disease or acute kidney injury, dialysis machines perform this essential function. Options A (stomach), B (liver), and C (brain) are incorrect because dialysis is not used to treat disorders of these organs.

Blood type O, particularly O-negative, is called the universal donor because individuals with this blood type can donate red blood cells to people with any other blood type (A, B, AB, or O). This is possible because O-type blood lacks A and B antigens on red blood cells that would trigger an immune response. Blood types A, B, and AB each have specific antigens that make them incompatible with universal donation. The 'a' in the question appears to be a typo.

Entomology is the scientific study of insects, including their behavior, physiology, classification, and ecology. The term derives from the Greek word 'entomon' meaning insect. The other options are incorrect: zoology is the broader study of all animals, ornithology is the study of birds, and odontology is the study of teeth and dental health.

Albert Einstein explained the photoelectric effect in 1905, showing that light behaves as discrete packets of energy (quanta/photons) rather than continuous waves. This groundbreaking work earned him the Nobel Prize in Physics in 1921. While Heinrich Hertz first observed the phenomenon in 1887, Einstein provided the theoretical explanation that revolutionized quantum physics. Faraday, Dalton, and Rutherford made important contributions to other areas of physics but not the photoelectric effect.

Sulfuric acid (H2SO4) is called the 'king of chemicals' because it is the most widely produced and used industrial chemical globally. It's essential for manufacturing fertilizers, chemicals, petroleum refining, and metal processing. The other options are incorrect: hydrochloric acid (HCl) is used in digestion and industry, nitric acid (HNO3) is important for explosives and fertilizers, and acetic acid (CH3COOH) is the main component of vinegar.

Melanin is the pigment responsible for giving color to skin, hair, and eyes. It's produced by specialized cells called melanocytes and provides protection against harmful UV radiation from the sun. The other options are incorrect: Nicotine is a stimulant found in tobacco, bilirubin is a waste product from red blood cell breakdown that causes jaundice, and hemoglobin is the red pigment in blood that carries oxygen (not responsible for baseline skin color).

Nitrous oxide (N2O) is commonly called 'laughing gas' because it causes euphoria and laughter when inhaled. It's used as an anesthetic and analgesic in medical and dental procedures. The other options are incorrect: carbon dioxide (CO2) is a greenhouse gas, vanadium pentoxide is used in sulfuric acid production, and hydrogen sulfide (H2S) is a toxic gas with a rotten egg smell.

High blood pressure (hypertension) is called the 'silent killer' because it typically has no symptoms until it causes serious damage to organs like the heart, brain, and kidneys. Millions of people have hypertension without knowing it. Low blood pressure (hypotension) is not typically lethal. Leukemia is blood cancer, and diabetes is an endocrine disorder - neither are called 'silent killers' in medical terminology.

Lithium is the lightest metal with an atomic number of 3 and atomic weight of approximately 6.94. It's an alkali metal that floats on water and is less dense than any other metal. The other options are incorrect: chromium is a transition metal, bromine is a liquid nonmetal (not a metal at all), and zinc is a transition metal - all are significantly heavier than lithium.

Aqua regia is the only solution that can dissolve gold. It is a mixture of concentrated nitric acid and hydrochloric acid in a 1:3 ratio, which produces reactive species that oxidize gold. Neither water nor any single acid like HCl or H2SO4 can dissolve gold.

Mercury is the only metal that is liquid at room temperature. Bromine is also liquid at room temperature, but it is a non-metal (halogen), not a metal. Hydrogen is a gas, and aluminum is a solid metal.

Ammonia is widely used in refrigeration plants and ice plants due to its excellent thermodynamic properties and low cost. It absorbs heat readily during evaporation, making it ideal for cooling applications. Noble gases like Xenon, Neon, and Argon are inert and not used in refrigeration.

Epsom salt is magnesium sulfate (MgSO4·7H2O). It is named after Epsom, England where it was originally obtained from mineral springs. The other options are different salts: potassium chloride, potassium nitrate, and ammonium carbonate.

Theodore Maiman built and demonstrated the first working laser in 1960 at Hughes Research Laboratories. While Charles Townes (misspelled as 'S towns') developed the maser (microwave amplifier), and others contributed to laser theory, Maiman created the first functional device using a ruby crystal.

The femur (thigh bone) is the longest and heaviest bone in the human body, typically about 50 cm long in adults. The 'born' in option A is a typo for 'bone'. The spine (back bone) consists of many small vertebrae, ribs form the ribcage, and ulna is a forearm bone.

Alfred Nobel invented dynamite in 1867 as a safer alternative to nitroglycerin. He established the Nobel Prize using his fortune from this and other inventions. C.V. Raman worked on light scattering, Edison on the light bulb and phonograph, and Fleming discovered penicillin.

The pituitary gland is called the 'master gland' because it produces hormones that regulate most other endocrine glands, including the thyroid, adrenal glands, and reproductive glands. It controls growth, metabolism, and reproduction through its hormonal signals.

Surface tension minimizes the surface area of a liquid for a given volume, causing water droplets to become spherical (a sphere has minimum surface area). Atmospheric pressure and gravitational force act externally, while 'capillary rice' is a typo for 'capillary rise' (a different phenomenon).

Dr. Jonas Salk developed the first successful polio vaccine in 1955. Note the name is misspelled as 'Johns E.Salk' and Louis Pasteur (misspelled as 'Paster') developed pasteurization and rabies vaccine. Edward Jenner created the smallpox vaccine.

Biogas primarily contains methane (50-75%), along with carbon dioxide and traces of other gases. Methane is the main combustible component that makes biogas useful as a fuel. Ethane, butane, and propane are higher hydrocarbons not typically found in significant amounts in biogas.