Red Blood Corpuscles (RBCs), also known as erythrocytes, are formed in the bone marrow. Specifically, they are produced in the red bone marrow of large bones through a process called erythropoiesis. The hormone erythropoietin, secreted mainly by the kidneys, regulates this process. Mature RBCs are responsible for transporting oxygen from the lungs to body tissues using the pigment hemoglobin.

Other options (for context)

• Heart: Pumps blood but does not produce blood cells.
• Liver: In adults, it does not form RBCs (though it does in the fetal stage).
• Kidney: Produces erythropoietin hormone but not RBCs directly.

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.

Nitrous oxide (N₂O) is an anaesthetic gas, commonly known as laughing gas. It is used in dentistry and minor surgeries to induce mild anesthesia and relaxation. It acts quickly and wears off rapidly, making it safe for short medical procedures.

• Nitrogen dioxide: A toxic air pollutant, not used as anesthesia.
• Nitric oxide: A signaling molecule in the body, not an anesthetic.
• Nitrogen: An inert gas, does not induce anesthesia.

Explanation: Ampicillin is a semi-synthetic derivative of penicillin and belongs to the β-lactam group of antibiotics. It inhibits bacterial cell wall synthesis and is effective against a wide range of gram-positive and gram-negative bacteria. Therefore, it is classified as a broad-spectrum antibiotic. Paracetamol is not an antibiotic, and penicillin is a narrow-spectrum antibiotic.

Explanation: Anaemia is a condition caused by a deficiency of iron in the body, leading to reduced formation of haemoglobin in red blood cells. As a result, the blood’s capacity to carry oxygen decreases, causing fatigue, weakness, dizziness, and pale skin. Iron is essential for haemoglobin synthesis, and deficiency can result from poor diet, blood loss, or malabsorption. Foods rich in iron include green leafy vegetables, liver, red meat, legumes, and jaggery.

Explanation: When a man inside a moving train tosses a coin and it falls behind him, it means the train is moving forward with acceleration. The coin, after being tossed, continues to move with the train’s initial velocity, but since the train speeds up, the coin appears to fall backward relative to the man.

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.

Explanation: Asbestos is a group of silicate minerals once used in insulation and construction materials. Inhalation of asbestos fibers causes severe lung disorders such as asbestosis and emphysema, leading to breathing difficulty, chest pain, and even lung cancer (mesothelioma). The fibers lodge in lung tissue and trigger inflammation and fibrosis over time.