A long silver teaspoon is placed in a cup filled with hot tea. After some time, the exposed end (the end which is not dipped in tea) of the spoon becomes hot even without direct contact with the tea. This phenomenon can be explained mainly by.............
A) Conduction
B) Reflection
C) Radiation
D) Thermal expansion

Hint: The exposed end (the end which is not dipped in tea) of the spoon becomes hot even without direct contact with the tea. This phenomenon can be explained by heat transmission in solid which is done by conduction in solids.

Complete step by step answer:
When one end of the spoon is dipped in a cup of hot tea then that end of the spoon takes heat from the heat by direct contact to heat. But the exposed end also gets hot because the heat can transmit inside the spoon hot end to cold end by conduction. In solids, heat can transmit by conduction.
Conduction is the process of heat transmission in which the particles of the body do not leave their position is called conduction.
In the above example when one end of the metallic spoon is kept in hot tea then Heat flows by conduction from the hot end of the spoon to the cold end as the result, the other end also becomes hot. according to kinetic theory molecules in the solid vibrate about their equilibrium positions and the amplitude of vibration depends upon the temperature of the solid when the temperature of one part of the solid increases then the amplitude of vibration of the molecules of this part increases these molecules give some energy to the adjacent part at the lower temperature.

Hence, the correct option A is correct.

Note:
Whenever there is a temperature difference between different part of the body, then the particles of the body at a higher temperature is given heat to the neighboring particle
There are three methods of heat transmission
1) Conduction – in solids
2) Convection – in liquid and gas
3) Radiation – by radiation sun to earth heat transmission.