Make a rule: how would you find the resistance of a parallel circuit with n identical resistors?

When n resistors are connected in parallel, it means they are connected to the same potential difference V:
(2)
It also means that the total current in the circuit is given by the sum of the currents flowing through each branch (each resistor) of the circuit:
(1)

By using Ohm's law:

we can rewrite (1) as

However, we said that the potential difference across each resistor is equal (eq.(2)), so we can rewrite the last formula as

From which we find an expression for the equivalent resistance of n resistors in parallel:

Ibelieve your answer is b.hope this : )