Explanation: Dengue fever is caused by the Dengue virus, which belongs to the Flavivirus group. It is transmitted to humans through the bite of an infected Aedes aegypti mosquito. The virus multiplies in the blood and causes symptoms such as high fever, severe headache, joint and muscle pain, rashes, and low platelet count. In severe cases, it can lead to Dengue hemorrhagic fever or Dengue shock syndrome. Prevention includes controlling mosquito breeding and avoiding mosquito bites.

Explanation: Athlete’s foot, scientifically known as Tinea pedis, is a fungal infection caused mainly by dermatophytes such as Trichophyton species. It thrives in warm, moist areas like the skin between the toes. Symptoms include itching, scaling, redness, and sometimes blistering. It spreads easily in communal areas like locker rooms and swimming pools. Proper hygiene and antifungal treatment can prevent and cure the infection.

Explanation: Ampicillin is a semi-synthetic derivative of penicillin and belongs to the β-lactam group of antibiotics. It inhibits bacterial cell wall synthesis and is effective against a wide range of gram-positive and gram-negative bacteria. Therefore, it is classified as a broad-spectrum antibiotic. Paracetamol is not an antibiotic, and penicillin is a narrow-spectrum antibiotic.

When an ant bites, it releases formic acid (HCOOH) into the skin. This acid causes a sharp burning sensation, redness, and irritation at the site of the bite. The name “formic” comes from the Latin word “formica”, meaning ant, as the acid was first extracted from ants. The pain can be neutralized by applying a mild base like baking soda (sodium bicarbonate).

Other options (for context)

• Hydrochloric Acid: Found in the human stomach, aids digestion.
• Acetic Acid: Main component of vinegar, not involved in ant bites.
• Phosphoric Acid: Used in fertilizers and soft drinks, not produced by ants.

Explanation: Red light is used in traffic signals because it has the longest wavelength among all visible colors. Due to this property, it gets scattered the least and can travel the farthest through fog, rain, or dust, making it easily visible from a long distance and ideal for indicating ‘stop’.

Coal is a fossil fuel formed from the remains of plants that lived and died millions of years ago. Over long geological periods, heat and pressure converted these plant remains buried under soil and rock into coal. It is a major source of energy used for electricity generation, steel production, and various industrial processes. However, burning coal releases carbon dioxide, contributing to air pollution and global warming.

Other options (for context)

• Solar energy: A renewable energy source derived from sunlight, not a fossil fuel.
• Quartz: A mineral composed of silicon and oxygen, not an energy source.
• Lava: Molten rock from volcanic eruptions, not a fossil fuel.

Explanation: Acupuncture is an ancient form of traditional Chinese medicine that involves the insertion of very thin needles through the skin at specific points, called acupoints. It is based on the concept of balancing the flow of life energy (Qi or Chi) through pathways in the body known as meridians. When these energy flows are blocked or imbalanced, it can cause illness or pain.

By stimulating specific acupoints, acupuncture is believed to restore the normal energy flow and help the body heal itself. It is commonly used to treat:

• Chronic pain (e.g., back, neck, and joint pain)
• Migraines and headaches
• Arthritis and muscle stiffness
• Stress and anxiety

Scientific View: Modern research suggests that acupuncture may stimulate nerves, muscles, and connective tissue, boosting the body’s natural painkillers (endorphins).

An Atom bomb works on the principle of nuclear fission. In this process, the nucleus of a heavy atom such as Uranium-235 or Plutonium-239 splits into two or more smaller nuclei when bombarded with a neutron. This splitting releases a tremendous amount of energy along with more neutrons, which further cause chain reactions — leading to a massive explosion.

Other options (for context)

• Chemical reaction: Produces far less energy; used in conventional explosives, not atomic bombs.
• Nuclear fusion: Powers hydrogen bombs (thermonuclear bombs), not atomic bombs.
• Atomic collision: General term — does not describe the chain reaction mechanism in fission.