William Harvey, an English physician, discovered the process of blood circulation in 1628. He demonstrated that the heart acts as a pump to circulate blood continuously throughout the body via a closed system of arteries and veins. His work, published in "De Motu Cordis" (On the Motion of the Heart and Blood), laid the foundation for modern cardiovascular physiology.

Other options (for context)

• Mary Anderson: Invented the windshield wiper, not related to medicine.
• Virginia Apgar: Developed the Apgar score for assessing newborn health.
• Robert Feulgen: Discovered a staining technique for DNA, not blood circulation.

Explanation: Carbon monoxide (CO) is a colorless, odorless, and highly poisonous gas. When inhaled, it competes with oxygen for binding sites on the haemoglobin molecule in red blood cells. CO has approximately 200–250 times greater affinity for haemoglobin than oxygen. As a result, it forms a stable compound called carboxyhaemoglobin (HbCO).

This compound prevents haemoglobin from carrying oxygen to body tissues, leading to oxygen deprivation (hypoxia). Prolonged exposure to CO can cause headache, dizziness, nausea, unconsciousness, and even death due to suffocation.

Chemical Reaction:

Hb + CO → HbCO (Carboxyhaemoglobin)

When iron rusts, its weight increases. This is because rusting is a chemical reaction between iron, oxygen, and moisture from the air, forming hydrated iron(III) oxide (Fe₂O₃·xH₂O). During this process, oxygen atoms from the air combine with the iron, adding extra mass to the metal surface in the form of rust. However, while the weight increases, the structural strength of the iron decreases due to corrosion.

Other options (for context)

• Decreases: Incorrect — mass increases due to the addition of oxygen.
• Remains the same: Incorrect — oxygen from air chemically adds to iron, increasing total mass.
• First increases and then decreases: Not applicable — in normal rusting, weight continues to increase until the surface flakes off.

The Green Revolution is associated with Agriculture. It refers to the period during the 1960s–70s when new technologies like high-yield variety (HYV) seeds, fertilizers, irrigation, and pesticides were introduced to boost food grain production, especially wheat and rice. It helped India achieve self-sufficiency in food production.

• Sericulture: Rearing of silkworms for silk.
• Fishery: Cultivation and harvesting of fish.
• Cultivation of bees: Known as apiculture, for honey production.

Explanation: Acupuncture is an ancient form of traditional Chinese medicine that involves the insertion of very thin needles through the skin at specific points, called acupoints. It is based on the concept of balancing the flow of life energy (Qi or Chi) through pathways in the body known as meridians. When these energy flows are blocked or imbalanced, it can cause illness or pain.

By stimulating specific acupoints, acupuncture is believed to restore the normal energy flow and help the body heal itself. It is commonly used to treat:

• Chronic pain (e.g., back, neck, and joint pain)
• Migraines and headaches
• Arthritis and muscle stiffness
• Stress and anxiety

Scientific View: Modern research suggests that acupuncture may stimulate nerves, muscles, and connective tissue, boosting the body’s natural painkillers (endorphins).

Explanation: When salt is added to pure water, its boiling point increases. This phenomenon is known as boiling point elevation, a colligative property. The presence of dissolved salt particles reduces the vapor pressure of water, requiring a higher temperature for it to boil.

Explanation: Tuberculosis (TB) is not a viral disease; it is caused by a bacterium called Mycobacterium tuberculosis. In contrast, Polio, Swine flu, and Hepatitis are viral diseases caused by different types of viruses.

Sustainable Development refers to growth that meets the needs of the present without compromising the ability of future generations to meet their own needs. It aims to balance economic progress, social equity, and environmental protection by conserving natural resources and reducing pollution for long-term ecological stability.

• Green economy: Focuses mainly on eco-friendly industries.
• Holistic development: Emphasizes overall human and social growth.
• Subsistence agriculture: Involves farming mainly for self-consumption.

Explanation: Web pages are written using HTML (HyperText Markup Language). It is the standard language used to create and structure content on the web by defining elements such as headings, paragraphs, links, images, and tables.