Explanation: Chikungunya is a viral disease caused by the Chikungunya virus, which belongs to the Togaviridae family. It is transmitted to humans through the bite of infected Aedes aegypti and Aedes albopictus mosquitoes. The disease causes sudden fever, joint pain, headache, and rash. In contrast, cholera (caused by Vibrio cholerae), typhoid (by Salmonella typhi), and tuberculosis (by Mycobacterium tuberculosis) are all bacterial diseases.

Explanation: Stars appear to twinkle at night due to the refraction of light by the Earth's atmosphere. As starlight passes through different layers of air with varying densities, its path bends continuously, causing the light’s intensity and position to appear to change, creating the twinkling effect.

Explanation: Although most non-metals do not conduct electricity, graphite is an exception. In graphite, each carbon atom is bonded to three others, leaving one free electron that moves freely between layers, allowing it to conduct electricity efficiently.

The Big Bang Theory explains the origin of the Universe. According to this theory, the universe began about 13.8 billion years ago from an extremely hot and dense state that expanded rapidly in all directions. This expansion continues even today, leading to the formation of galaxies, stars, planets, and other cosmic structures. The discovery of the cosmic microwave background radiation provides strong evidence supporting the Big Bang Theory.

Other options (for context)

• Origin of Sun: Explained by the Nebular Hypothesis, not the Big Bang Theory.
• Laws of Chemistry: Studied under physical and inorganic chemistry, unrelated to cosmology.
• Laws of History: Concern human civilizations, not the universe’s formation.

Explanation: The full form of GPS is Global Positioning System. It is a satellite-based navigation system that provides accurate information about the location, speed, and time anywhere on Earth. Developed by the U.S. Department of Defense, GPS uses a network of at least 24 satellites orbiting the Earth. It is widely used in navigation, mapping, military operations, aviation, and smartphone tracking applications.

Explanation: LCD stands for Liquid Crystal Display. It is a flat-panel display technology commonly used in televisions, computer monitors, calculators, and smartphones. LCDs use liquid crystals that modulate light to produce images when an electric current is applied.