Explanation: Oncology is a branch of medical science that focuses on the study, diagnosis, treatment, and prevention of cancers and tumours. The term is derived from the Greek word “onkos” meaning mass or tumour. A specialist in this field is called an Oncologist.

Major Branches of Oncology:

• Medical Oncology: Treatment using chemotherapy, targeted therapy, and immunotherapy.
• Surgical Oncology: Removal of tumours through surgery.
• Radiation Oncology: Treatment of cancer using radiation therapy.

Common Cancers Studied in Oncology: Lung cancer, breast cancer, skin cancer, leukemia (blood cancer), and prostate cancer.

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.

The Taj Mahal is threatened primarily due to sulphur dioxide (SO₂) pollution. When sulphur dioxide released from nearby industries and vehicles mixes with moisture in the air, it forms sulphuric acid, leading to acid rain. This acid rain reacts with the white marble of the Taj Mahal, causing it to turn yellow and deteriorate — a phenomenon known as “Marble Cancer.”

Other options (for context)

• Carbon dioxide: Contributes to global warming but does not directly damage marble.
• Carbon monoxide: Harmful to health but has minimal effect on marble structures.
• Water vapour: Naturally present in the atmosphere and not harmful to monuments.

Explanation: The DNA sequencing technique was developed by Frederick Sanger in 1977. His method, known as the Sanger chain termination method, determines the nucleotide sequence of DNA using labeled dideoxynucleotides (ddNTPs) that terminate DNA chain elongation. This technique revolutionized molecular biology and became the foundation for genome sequencing projects such as the Human Genome Project.

Explanation: The thyroid gland is located in the neck region, just below the larynx (voice box) and in front of the trachea (windpipe). It is a butterfly-shaped endocrine gland that secretes the hormones thyroxine (T₄) and triiodothyronine (T₃). These hormones regulate metabolism, growth, and energy production in the body. The thyroid also produces calcitonin, which helps control calcium levels in the blood. Iodine is essential for the synthesis of thyroid hormones.

Explanation: The burning of a candle is a chemical change because new substances such as carbon dioxide, water vapour, and heat energy are produced during the reaction between wax and oxygen. This change is irreversible and results in a permanent alteration of the chemical composition of the material. In contrast, melting of wax and vapourisation of water are physical changes since no new substances are formed and the process can be reversed by cooling.

Explanation: The star rating system seen on electrical appliances (like ACs, refrigerators, and fans) represents the energy efficiency of the product. It is issued by the Bureau of Energy Efficiency (BEE), under the Ministry of Power, Government of India. The more the number of stars (up to 5), the higher the energy efficiency — meaning the appliance consumes less electricity for the same performance. However, the star rating does not indicate the lifespan or the quality checks of the appliance.

Explanation: The term LASER stands for Light Amplification by Stimulated Emission of Radiation. A laser produces a highly coherent, monochromatic, and intense beam of light by amplifying light through the process of stimulated emission. In this process, atoms or molecules in an excited state emit photons in phase with incoming photons, resulting in a strong, directed beam. Lasers are widely used in medicine, communication, industry, defense, and scientific research.

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 lens is generally made of flint glass, which contains lead oxide. Flint glass has a higher refractive index than ordinary glass, allowing it to bend light more effectively. This property makes it ideal for manufacturing optical instruments such as lenses and prisms.