Heat can be transferred in the three different methods mentioned in the question: conduction, convection, radiation.
Conduction is the transfer of heat that occurs when two substances are in direct physical contact. The particles in one substance are heated, causing them to gain more energy and vibrate more rapidly. The particles then collide into neighbouring particles and transfer energy to them. An example would be placing your hand on a heated element on a stove top.
Radiation is does not require any contact between particles and the heat can be transferred through space through thermal radiation such as infrared radiation. There is no medium or mass necessary during radiation. An example would be the heat we feel from the sun.
These two processes do not appear to apply to the examples given. Therefore, the answer is b) convection currents transfer.
Convection is the transfer of thermal energy from hot areas to colder areas. Specifically when a warm area of gas or liquid rises to a colder area. The cooler particles of liquid or gas will displace the warmer particles which have risen, creating a continuous current.
