Explanation: Proteins are complex organic compounds composed of smaller units called amino acids. Each amino acid contains an amino group (–NH₂), which contributes nitrogen to the molecular structure. This makes nitrogen an essential element in all proteins. Carbohydrates and fats lack nitrogen, while only some vitamins contain it.

Adolf Gaston Eugen Fick, a German physiologist, invented the first successful contact lens in 1888. His design consisted of a glass lens that covered the entire eye, resting on the sclera (the white part of the eye). Though bulky and uncomfortable by today’s standards, it laid the foundation for modern soft and gas-permeable contact lenses used in vision correction and cosmetics.

Other options (for context)

• Enrico Fermi: Known for his work in nuclear physics and development of the first nuclear reactor.
• Sandford Fleming: Introduced the concept of standard time zones.
• Benoit Fourneyron: Invented the water turbine, not related to optics or vision correction.

The electron was discovered by J. J. Thomson in 1897 during his experiments with cathode rays. He demonstrated that cathode rays are composed of tiny negatively charged particles, which he named electrons. This discovery revolutionized atomic theory and led to the development of the plum pudding model of the atom, where electrons are embedded in a positively charged sphere.

Other options (for context)

• Enrico Fermi: Known for his work on nuclear physics and the development of the first nuclear reactor.
• Robert Noyce: Co-inventor of the integrated circuit (microchip).
• James Dyson: Inventor of the modern vacuum cleaner, not a physicist.

Explanation: A fan provides a feeling of comfort during hot weather because it increases the rate of evaporation of sweat from our skin. As the perspiration evaporates rapidly due to moving air, it absorbs heat from the body, producing a cooling effect and making us feel more comfortable.

Explanation: Edward Jenner, an English physician, is known as the “Father of Immunology.” In 1796, he observed that milkmaids who had previously suffered from cowpox (a mild disease) did not contract smallpox (a deadly viral disease). He tested his hypothesis by injecting a boy with material taken from a cowpox sore and later exposing him to smallpox — the boy did not develop the disease. This led to the development of the first vaccine, derived from the Latin word vacca meaning “cow.”

Significance: Jenner’s discovery laid the foundation of modern immunology and preventive medicine. Smallpox was officially declared eradicated by the WHO in 1980.

Explanation: Tuberculosis (TB) is not a viral disease; it is caused by a bacterium called Mycobacterium tuberculosis. In contrast, Polio, Swine flu, and Hepatitis are viral diseases caused by different types of viruses.

Explanation: The Growth Hormone (GH), also known as Somatotropin, is secreted by the anterior lobe of the pituitary gland, which is located at the base of the brain. This hormone stimulates growth, cell reproduction, and regeneration in humans and other animals. It plays a vital role in increasing height during childhood and adolescence, regulating metabolism, and maintaining muscle and bone mass. A deficiency of GH causes dwarfism in children, while excess secretion leads to gigantism or acromegaly.

Explanation: The nephron is the basic structural and functional unit of the kidney. Each human kidney contains about 1 to 1.5 million nephrons. A nephron consists of two main parts — the renal corpuscle (Bowman's capsule and glomerulus) and the renal tubule. It performs three main functions: filtration of blood, reabsorption of essential substances, and secretion