Answer:
Option A: Solids
Step-by-step explanation:
Due to the fact that heat is transported from a hotter body to a cooler body when two objects are kept in thermal contact, conduction only occurs in solids and not in liquids or gases. Conduction is the term for this mechanism, which uses the same body temperature. When two bodies remain together during conduction to transfer heat In order to transmit heat energy quickly and more efficiently, the molecules of both entities vibrate and collide with one another. Since solids have compactly packed molecules, this allows the molecules to vibrate more and transfer heat more effectively than liquids and gases. When molecules in close proximity to one another clash, energy is transferred. Due to the molecules' near closeness and, in the case of crystals, their clearly defined structure, this occurs very readily in a solid. A few things alter when heat transport in liquids and gases is taken into account. The molecules are not as close together, and gravity has a particular, confusing influence. Heat is transferred through collisions of nearby particles in a process known as convection. The metal surface particles are transmitting heat to the liquid through conduction at the metal-water interface if convection is occurring between a solid that is hotter than the liquid adjacent to it, such as a pan on the stove. But when that occurs, the water's density begins to alter. The water molecules at the surface move faster, contain more energy, and occupy more space per mass (they are less dense). Because water molecules may pass one another and gravity makes this easier, the less dense water near the metal surface is replaced by the more dense water above it. Natural convection is the mechanism through which a liquid or gas moves in this manner as a result of variations in density. Conduction is no longer possible unless you can prevent the effect of fluid density on the flow of gases or liquids. Fundamentally, in both liquids and gases as well as solids, molecules continue to exchange energy through collisions. Conduction, however, performs this considerably more effectively in liquids at the metal-liquid contact and less so as you travel away from the interface and upward through the liquid. Convection is the movement of particles to transfer heat.
Bottom Line: Conduction may occur in gases and liquids, but you must be able to reduce the impact of gravity. These are known as "stagnant fluids." Convection is the term used to describe fluid movement caused by density variations when they are not prevented.