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.

Explanation: A strong-smelling compound called thioethanolamine (or ethyl mercaptan) is added to LPG (liquefied petroleum gas) to help detect gas leaks. LPG itself is odourless, so this compound gives it a distinct unpleasant smell, making leakage easily noticeable for safety.

Explanation: Shadows are formed when an opaque object comes in the path of light. Opaque objects do not allow light to pass through them, causing a dark region called a shadow to form on the opposite side. Transparent and translucent objects allow light to pass fully or partially, so they form faint or no shadows.

Explanation: Penicillin was discovered accidentally by Alexander Fleming in 1928 when he observed that a fungal mold, Penicillium notatum, inhibited the growth of Staphylococcus bacteria in his culture plates. Penicillin became the first antibiotic used to treat bacterial infections and saved millions of lives during World War II. Later, scientists like Howard Florey and Ernst Boris Chain developed methods for its large-scale production.

Silver is the best conductor of heat among the given options. It efficiently transfers heat due to the presence of free electrons that move easily within its metallic structure. Because of this property, silver is used in high-quality thermal equipment and electrical contacts.

• Mercury: A metal but conducts heat less effectively than silver.
• Leather and Benzene: Poor conductors of heat (insulators).

Explanation: Opium is obtained from the latex present in the unripe capsule of the poppy plant (Papaver somniferum). The latex is collected by making incisions on the capsule, and after drying, it forms raw opium, which contains alkaloids like morphine and codeine.

Explanation: Mesons are subatomic particles found in cosmic rays. They are unstable particles composed of one quark and one antiquark, making them part of the hadron family. Mesons are produced when high-energy cosmic rays from outer space collide with atoms in the Earth's atmosphere. These collisions generate a variety of secondary particles, including pions and kaons (types of mesons). Mesons have very short lifespans and quickly decay into other particles such as muons and neutrinos.

Explanation: The audible range of sound refers to the frequencies that can be detected by the average human ear, typically from 20 Hz to 20,000 Hz (20 kHz). Sounds below 20 Hz are called infrasonic and those above 20,000 Hz are called ultrasonic. Hearing sensitivity decreases with age, and most adults can hear up to about 16,000 Hz.

Aryabhatta was a renowned mathematician and astronomer of ancient India. He lived during the Gupta period (around 476–550 CE) and authored the famous work Aryabhatiya. Aryabhatta introduced the concept of zero (0) and explained the place value system. He also proposed that the Earth rotates on its axis and correctly explained solar and lunar eclipses.

Other options (for context)

• Doctor: No historical evidence of Aryabhatta being a physician.
• Poet: Although his works were written in verse form, his main field was mathematics and astronomy.
• Physicist: The term did not exist in his time; however, his scientific thinking laid foundations for later studies.