Which material is the best conductor?
(A). Silver
(B). Porcelain
(C). Rubber
(D). Gold

Hint: Before attempting this question one should have prior knowledge about the conductor such as how the conductor helps the current to travel, using this information will help you to approach towards the solution to the question.

 Complete step-by-step solution -
Before discussing the conducting property shown by the materials given in the question, let’s first talk about what are conductors?
So the conductor is a property of a material which helps the motion of the electric current through it generally conducting property is shown by the metals like copper, iron, etc.
Let’s discuss about the conducting property of the materials given in question
Silver
Silver is a metal which have the best conducting property than all the metals because of its great number of free electrons so when the electric current is passed through the silver its electrons moves due to which the conduction of electricity takes place and due to its high amount of free electron makes it the best conductor of all metal
Porcelain
It is a material made by the clay by heating it in high temperature which makes it an insulator and in insulator there are no free electron which can help electricity to move in porcelain thus it is not a conductor
Rubber
It is an insulator and an elastic substance made from juice from trees and also produced chemically it is also the best insulator from all materials. Therefore it is also not a good conductor
Gold
Gold is a metal which is also a good conductor but its conducting property is lower than copper and silver because of its chemical stability which make it conductivity property lower than the silver and copper like materials.
So since from all the materials given silver shows the best conducting property therefore silver is the best conductor among all given materials
Hence option A is the correct option.

Note: As we observed in the above solution that the insulators are not able to conduct the electricity and all the insulator are non-metal and almost all the conductor are metal but there is a non-metal exist which is a good conductor of electricity i.e. graphite which conducts electricity because of its delocalized electrons present in it same as metal these delocalized electrons moves between the layers of graphite and conducts electricity.