Explanation: Measles is a highly contagious viral disease caused by the measles virus (a member of the Paramyxovirus group). It spreads through droplets released when an infected person coughs or sneezes. Symptoms include fever, cough, rash, and watery eyes. Other diseases listed — scurvy, asthma, and diabetes — are non-communicable as they do not spread from person to person.

Explanation: Malaria and Trichomoniasis are both protozoan diseases, not bacterial. Malaria is caused by Plasmodium species (transmitted by female Anopheles mosquitoes), while Trichomoniasis is caused by Trichomonas vaginalis, a sexually transmitted protozoan infection. Unlike bacterial diseases, these are treated using antiprotozoal drugs rather than antibiotics.

The Widal test is used to diagnose Typhoid fever, a bacterial infection caused by Salmonella typhi. The test detects the presence of agglutinating antibodies (O and H) in a patient’s serum against the antigens of the typhoid bacteria. It helps confirm infection during the second week of illness.

• Cholera: Diagnosed by stool culture for Vibrio cholerae.
• Tuberculosis: Detected using sputum test or Mantoux test.
• AIDS: Diagnosed through ELISA or Western blot test for HIV.

All of the above are examples of static electricity. Static electricity is the result of the accumulation of electric charges on the surface of objects. When materials like glass, silk, ebonite, or wool are rubbed together, electrons are transferred, creating a charge imbalance. Similarly, lightning is a large-scale natural discharge of static electricity between clouds and the Earth.

• Glass rod & silk cloth: Positive and negative charges develop.
• Ebonite rod & wool: Negative charge accumulates on ebonite.
• Lightning: Discharge of atmospheric static electricity.

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.

Explanation: The transmission of light through optical fibres is based on the principle of Total Internal Reflection (TIR). When light travels from a denser medium (core of the fibre) to a rarer medium (cladding) and strikes the interface at an angle greater than the critical angle, it gets completely reflected back into the core instead of refracting out. This continuous internal reflection allows light to travel long distances through the fibre with minimal loss, even when the fibre is bent. Optical fibres are widely used in telecommunication, internet data transfer, and medical endoscopy.

Explanation: Below the critical temperature, gases can be liquefied by applying pressure because the intermolecular forces of attraction between gas molecules become effective. These forces pull the molecules closer together, resulting in the formation of a liquid state.

Explanation: In GM food, the term GM stands for Genetically Modified. These are foods produced from organisms (plants or animals) whose genetic material (DNA) has been altered using modern biotechnology or genetic engineering techniques. This modification is done to introduce desirable traits such as pest resistance, drought tolerance, higher yield, or improved nutritional value. A common example is Bt cotton, which contains a gene from the bacterium Bacillus thuringiensis that provides resistance to insect pests.

A Lunar Eclipse occurs when the Earth comes between the Sun and the Moon, causing the Earth’s shadow to fall on the Moon. This alignment blocks the sunlight that normally reflects off the Moon’s surface, making it appear dark or reddish (known as a Blood Moon). Lunar eclipses only occur during a full moon when the Sun, Earth, and Moon are in a straight line (or nearly so).

Other options (for context)

• When Sun is between Earth and Moon: Incorrect — this alignment causes no eclipse.
• When Moon is between Earth and Sun: This alignment causes a solar eclipse, not a lunar one.
• When Earth is between Sun and other celestial bodies: Too general — lunar eclipse specifically involves the Moon.