Explanation: Electromagnetic waves can propagate even through a vacuum because they do not require any material medium for transmission. Examples include light waves, radio waves, X-rays, and microwaves. In contrast, mechanical waves like sound require a medium such as air, water, or solids to travel.

Explanation: A fan provides a feeling of comfort during hot weather because it increases the rate of evaporation of sweat from our skin. As the perspiration evaporates rapidly due to moving air, it absorbs heat from the body, producing a cooling effect and making us feel more comfortable.

Tuberculosis (TB) is commonly known as the "White Plague". It earned this name because it causes extreme paleness and weight loss in affected individuals. Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis, primarily affecting the lungs but can also spread to other parts of the body. It spreads through airborne droplets when an infected person coughs or sneezes.

Other options (for context)

• Typhoid: Caused by Salmonella typhi, affects the intestine and causes high fever.
• Malaria: Caused by Plasmodium parasite transmitted through mosquito bites.
• Plague: Caused by Yersinia pestis, historically known as the “Black Death,” not the white plague.

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.

Explanation: The Curie point (or Curie temperature) is the temperature above which a ferromagnetic material loses its magnetic properties and becomes paramagnetic. At this point, thermal energy overcomes the magnetic alignment of atoms. For example, the Curie temperature of iron is about 770°C.

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: Fathom is a unit used to measure depth, particularly the depth of water in oceans and seas. One fathom is equal to 6 feet or approximately 1.83 meters. It is commonly used in navigation and marine studies.