Explanation: Marijuana is a psychoactive drug obtained from the female inflorescence (flowering tops) of the Cannabis sativa plant. It contains the active compound tetrahydrocannabinol (THC), which affects the central nervous system and alters mood and perception.

Explanation: Cadmium (Cd) is a toxic heavy metal released from industrial waste, batteries, and mining processes. When it enters the food chain (especially through contaminated rice or water), it accumulates in the body and affects the kidneys, causing protein loss in urine and kidney failure. It is also associated with Itai-Itai disease in Japan, characterized by kidney damage and brittle bones.

Explanation: The main function of the kidneys is to purify blood by removing waste products, excess salts, and extra water from the body in the form of urine. Each kidney contains about one million nephrons, which are the structural and functional units responsible for blood filtration. The kidneys also help in maintaining the acid-base balance, water balance, and blood pressure, and play a role in hormone secretion such as erythropoietin (for RBC production).

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: Measles is a highly contagious viral disease caused by the measles virus (a member of the Paramyxovirus group). It spreads through droplets released when an infected person coughs or sneezes. Symptoms include fever, cough, rash, and watery eyes. Other diseases listed — scurvy, asthma, and diabetes — are non-communicable as they do not spread from person to person.

The Ramsar Convention is an international treaty for the conservation and sustainable use of wetlands. Signed in 1971 at Ramsar, Iran, it aims to preserve wetlands as habitats for biodiversity, especially for migratory birds. It promotes wise use of wetland ecosystems through local and national actions.

• Mountain: Conserved under other ecological programs.
• Grassland: Managed under terrestrial biodiversity initiatives.
• Forest: Covered under the UN Forest Forum, not Ramsar.

Explanation: Rakesh Sharma was the first Indian astronaut to travel into space. He flew aboard the Soviet spacecraft Soyuz T-11 on April 3, 1984, as part of a joint mission between ISRO (Indian Space Research Organisation) and the Soviet Intercosmos program. During his space mission, he spent about 8 days aboard the Salyut-7 space station. When asked by then Prime Minister Indira Gandhi how India looked from space, he famously replied, “Saare Jahan Se Achha.”

Glaciers usually melt first at the bottom. The pressure at the base of a glacier is very high, which lowers the melting point of ice — a phenomenon known as pressure melting. Additionally, heat from the Earth’s crust and friction caused by glacier movement also contribute to faster melting at the base.

• Top surface: Exposed to air but melts slower due to lower pressure.
• Sides and middle surface: Experience less pressure and friction, so melting is slower.

Explanation: Fibrinogen is a soluble plasma protein produced by the liver. During blood clotting, it is converted into insoluble fibrin threads by the enzyme thrombin. These fibrin threads form a mesh that traps red blood cells and platelets, creating a stable clot to stop bleeding. This process prevents excessive blood loss during injury and is regulated by clotting factors and platelets.

Simplified Reaction:

Fibrinogen → (Thrombin) → Fibrin → Blood Clot