. Which of the following cannot be charged easily by friction
A: A plastic scale
B: A copper rod
C: An inflated balloon
D: A woollen cloth
Through friction only non-conductors can be charged.
So, from the given option it is known that Copper rod is a conductor.
So, Copper rod cannot be charged by friction as it is a conductor.
So, option (B) is correct.
Hence, option (B) is correct.