Explanation: Hardware refers to the physical components of a computer that can be seen and touched, such as the monitor, keyboard, mouse, CPU, and printer. In contrast, software consists of programs and instructions that control the hardware and perform tasks.

Explanation: Humans first develop a set of 20 milk teeth (also called deciduous or primary teeth) — 10 in the upper jaw and 10 in the lower jaw. These teeth start erupting around 6 months of age and are eventually replaced by 32 permanent teeth (including 4 wisdom teeth). Milk teeth help in early chewing, speaking, and maintaining space for permanent teeth.

Marble is not an element; it is a metamorphic rock composed primarily of calcium carbonate (CaCO₃). It forms when limestone is subjected to high pressure and temperature, causing recrystallization. Being a compound and mixture of minerals, marble does not consist of a single type of atom, unlike elements.

Other options (for context)

• Oxygen (O₂): A chemical element essential for respiration and combustion.
• Nitrogen (N₂): A chemical element that makes up about 78% of Earth’s atmosphere.
• Hydrogen (H₂): The lightest chemical element and the main component of stars.

Explanation: A monitor is an output device that displays text, images, and videos generated by the computer. It allows users to visually view the processed data. Common types of monitors include LCD, LED, and OLED screens.

Explanation: Among the given particles, the proton is the heaviest. A proton is a positively charged subatomic particle found in the nucleus of an atom, with a mass of approximately 1.672 × 10⁻²⁷ kg. Although the neutron is slightly heavier than a proton, in most general questions like this one, protons are considered heavier in context when compared with electrons and neutrinos. Electrons are much lighter, with a mass about 1/1836 that of a proton, while neutrinos are nearly massless and electrically neutral.

Explanation: In fused (molten) sodium chloride, electric current passes due to the presence of free ions. When solid NaCl is melted, it dissociates into Na⁺ and Cl⁻ ions, which can move freely and conduct electricity. In the solid state, these ions are fixed in the crystal lattice, so it does not conduct electricity.

In India, the most widely used form of renewable energy is Solar Energy. Due to the country’s tropical location, India receives abundant sunlight throughout the year, making solar power a highly viable and sustainable energy source. It is harnessed using solar panels for electricity generation and heating applications under initiatives like National Solar Mission.

• Geothermal energy: Used only in limited pilot projects.
• Hydro-electric energy: Important but not as rapidly expanding as solar.
• Thermal energy: Usually refers to non-renewable coal-based power plants.

Explanation: Inside a sealed pressure cooker, the pressure is higher than atmospheric pressure, which raises the boiling point of water to about 121℃. This allows food to cook faster because water and steam reach higher temperatures than at normal atmospheric pressure.

Explanation: The femur is the single bone of the thigh region and extends from the hip joint to the knee joint. It supports the body’s weight during standing, walking, and running. The femur is the longest, heaviest, and strongest bone in the human skeleton. It articulates with the pelvic girdle at its proximal end (head of femur fits into the acetabulum of the pelvis) and with the tibia and patella at the distal end.

Average Length: Approximately 45 cm (about 1/4 of body height).