(A): Most of good conductors of heat are also good conductors of electricity and vice versa.
(R): Mainly electrons are responsible for these conductions. 

Options

A. Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'
B. Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'
C. 'A' is true and 'R' is false
D. 'A' is false and 'R' is false

Answer

A