Explanation: Entomology is a branch of Zoology that focuses on the study of insects, including their structure, classification, behavior, ecology, and evolution. Insects make up more than 75% of all known animal species on Earth and play crucial roles in pollination, decomposition, and food chains. Scientists who study insects are known as entomologists.

Explanation: Sound travels fastest in steel because it is a solid material where the particles are packed very closely together. Sound waves need a medium to travel, and their speed depends on how quickly vibrations can pass from one particle to another. In solids, particles are tightly bound, so vibrations are transmitted more efficiently. In contrast, sound travels slower in liquids and slowest in gases. It cannot travel through a vacuum because there are no particles to carry the vibrations.

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: When a car moves forward while rain is falling vertically, the rain appears to fall at an angle relative to the car’s motion. As a result, the raindrops strike the front windscreen of the car, not the rear screen. This is due to the relative velocity between the car and the falling rain.

Explanation: A transformer is an electrical device used to increase (step-up) or decrease (step-down) the voltage of alternating current (A.C.). It works on the principle of electromagnetic induction and functions only with A.C., not with D.C. A transformer consists of two coils—primary and secondary—wound around a soft iron core. The voltage ratio between these coils depends on the number of turns in each winding. Transformers are used in power transmission, distribution, and electronic devices to regulate voltage levels efficiently.

Deciduous trees are those that shed all their leaves once a year, usually during the dry or winter season to conserve water and energy. After a period of dormancy, they grow new leaves at the beginning of the next growing season. Common examples include teak, sal, neem, and peepal. This adaptation helps the trees survive unfavorable climatic conditions.

Other options (for context)

• Coniferous trees: Mostly evergreen and do not shed all their leaves at once; examples include pine and deodar.
• Evergreen trees: Retain their leaves throughout the year and shed them gradually.
• Both deciduous and coniferous trees: Incorrect — only deciduous trees completely shed their leaves annually.

Explanation: Leguminous crops such as peas, beans, gram, and clover have a symbiotic relationship with Rhizobium bacteria in their root nodules. These bacteria convert atmospheric nitrogen into ammonia, enriching soil fertility naturally. Hence, legumes are used in crop rotation to restore nitrogen content in soil.

Explanation: Aerosols (such as those used in spray cans, refrigerants, and air conditioners) often contain chlorofluorocarbons (CFCs) and other halogen compounds. These chemicals rise to the stratosphere, where ultraviolet (UV) radiation breaks them down, releasing chlorine atoms. Each chlorine atom can destroy thousands of ozone (O₃) molecules, leading to ozone layer depletion. The thinning of the ozone layer allows more harmful UV rays to reach Earth, increasing the risk of skin cancer, eye damage, and affecting ecosystems.