A 3 ohm resistor having 2 A current will dissipate the power of

The correct answer is B. 4 watts.

The power dissipated by a resistor is given by the formula $P = I^2R$, where $I$ is the current through the resistor and $R$ is the resistance of the resistor. In this case, $I = 2 A$ and $R = 3 \Omega$, so the power dissipated is $P = (2 A)^2(3 \Omega) = 4 W$.

Option A is incorrect because it is the power dissipated by a 2 ohm resistor with 2 A current. Option C is incorrect because it is the power dissipated by a 6 ohm resistor with 2 A current. Option D is incorrect because it is the power dissipated by an 8 ohm resistor with 2 A current.