Nickel exposure commonly causes a skin disease called Dermatitis, specifically Allergic Contact Dermatitis. This condition occurs when the skin comes into direct contact with nickel-containing objects such as jewelry, coins, or belt buckles. It leads to redness, itching, and rashes, especially in sensitive individuals. Nickel allergy is one of the most common metal allergies worldwide.

Other options (for context)

• Itai Itai: Caused by cadmium poisoning, not nickel.
• Learning Disability: Not directly linked to nickel exposure.
• Asthma: May be aggravated by pollutants, but not typically caused by nickel.

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 statement “Exercise does not help in managing psychological discomfort” is incorrect. Regular physical exercise helps reduce stress, anxiety, and depression by releasing endorphins — the body’s natural mood enhancers. It also improves overall mental health, cardio-respiratory fitness, reduces the risk of diabetes, and strengthens bones.

Explanation: Prithvi was the first indigenously developed missile of India, designed under the Integrated Guided Missile Development Programme (IGMDP) launched in 1983 by the Defence Research and Development Organisation (DRDO). It is a surface-to-surface short-range ballistic missile (SRBM) capable of carrying both conventional and nuclear warheads. The Prithvi missile series includes Prithvi-I (Army version), Prithvi-II (Air Force), and Prithvi-III (Navy), with ranges varying from 150 km to 350 km.

Sir Isaac Newton invented the Reflecting Telescope in 1668. Unlike earlier refracting telescopes that used lenses, Newton’s design used a concave mirror to reflect and focus light. This eliminated chromatic aberration (color distortion) caused by lenses and significantly improved image clarity. Newton’s reflecting telescope became a major advancement in astronomical observation.

Other options (for context)

• Thermometer: Invented by Galileo Galilei (early version) and later improved by Daniel Gabriel Fahrenheit.
• Hydraulic Accumulator: Invented by William Armstrong.
• Transistor: Invented much later (in 1947) by John Bardeen, William Shockley, and Walter Brattain.

Explanation: The chemical name of baking powder is sodium bicarbonate (NaHCO₃), also known as baking soda. It is a mild alkali used in cooking and baking as a leavening agent. When heated or mixed with an acid (like vinegar, lemon juice, or cream of tartar), it decomposes to release carbon dioxide gas (CO₂). The bubbles of CO₂ make the dough rise and become soft and spongy. In commercial baking powder, sodium bicarbonate is often mixed with a weak acid and a drying agent.

Explanation: The main function of the kidneys is to purify blood by removing waste products, excess salts, and extra water from the body in the form of urine. Each kidney contains about one million nephrons, which are the structural and functional units responsible for blood filtration. The kidneys also help in maintaining the acid-base balance, water balance, and blood pressure, and play a role in hormone secretion such as erythropoietin (for RBC production).

The O blood group, specifically O negative (O−), is considered the Universal Donor because it can be safely transfused to people of all other blood groups. This is due to the absence of A and B antigens on red blood cells, minimizing the risk of immune reactions during transfusion.

• A: Can donate only to A and AB groups.
• AB: Universal recipient, not donor.
• B: Can donate only to B and AB groups.