Metals can be beaten into thin sheets because they are malleable. Malleability is a physical property of metals that allows them to withstand hammering or rolling without breaking. This property is due to the metallic bonding where positive metal ions are surrounded by a ‘sea’ of delocalized electrons, allowing the layers of atoms to slide over each other without breaking the bond. Examples of highly malleable metals include gold, silver, and aluminium.

Other options (for context)

• Ductile: Refers to the ability of metals to be drawn into wires, not beaten into sheets.
• Soft: Not true for all metals — many are hard yet malleable.
• Loosely arranged particles: Incorrect — metal atoms are closely packed in a lattice structure.

Explanation: Ecology is a branch of biology that deals with the relationships of living organisms with one another and with their physical surroundings. It examines how organisms adapt to their environment, how energy flows through ecosystems, and how matter cycles within the biosphere. The term “Ecology” was first coined by Ernst Haeckel in 1866.

Explanation: In a parallel connection of resistances, the potential difference (voltage) across each resistor remains the same, while the current divides among the different branches according to their resistances. This property makes parallel circuits widely used in household electrical wiring.

Explanation: Below the critical temperature, gases can be liquefied by applying pressure because the intermolecular forces of attraction between gas molecules become effective. These forces pull the molecules closer together, resulting in the formation of a liquid state.

Explanation: Mumps is a contagious viral disease caused by the mumps virus, a member of the Paramyxoviridae family (genus Rubulavirus). It primarily affects the salivary glands, especially the parotid glands, leading to painful swelling near the cheeks and jawline.

Mode of Transmission: The infection spreads through respiratory droplets or direct contact with saliva from an infected person.

Symptoms:

• Swelling and pain in the parotid glands (below the ears)
• Fever and headache
• Muscle pain and fatigue
• Difficulty in chewing or swallowing

Prevention: Mumps can be effectively prevented by the MMR vaccine (Measles, Mumps, and Rubella vaccine).

Explanation: Electrons are negatively charged particles that revolve around the nucleus in fixed paths called orbits or shells. The nucleus contains positively charged protons and neutral neutrons, and most of the atom’s mass is concentrated in the nucleus.

Explanation: Normal human blood has a slightly alkaline pH of 7.35 to 7.45. This pH is maintained by buffer systems such as the bicarbonate buffer system and controlled by the lungs (CO₂ regulation) and kidneys (acid-base balance). A deviation from this range can be life-threatening — acidosis occurs if pH falls below 7.35, and alkalosis occurs if it rises above 7.45.

Explanation: During photosynthesis, green plants use sunlight to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂). The oxygen gas released in this process comes specifically from the splitting of water molecules — a reaction known as photolysis of water, which occurs in the light-dependent reaction inside the chloroplasts.

Chemical equation:

6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O

The oxygen atoms in the released O₂ come entirely from the original water molecules, as demonstrated by isotopic experiments using heavy oxygen (O¹⁸) tracers.