Ohm's unit from power-current relation Steps:

• Resistance R = V / I from Ohm's law, with V in volts and I in amperes.
• Power P = V I, so V = P / I = W / A.
• Substitute: R = (W / A) / A = W A^{-2}.
• This expresses ohm using watt (derived from base units kg m² s^{-3}) and ampere.

Why D is correct:

• From P = I² R, R = P / I² = W A^{-2}, matching the dimensional formula kg m² s^{-3} A^{-2}.

Why the others are wrong:

• A: kg m^{-2} s^{-2} has incorrect exponents (lacks s^{-3}, A^{-2}; resembles inverse permittivity units).
• B: kg m² s^{-3} A^{-1} is the base unit expression for volt (V).
• C: A^{-1} is the base unit for electrical conductance (1/Ω, or siemens).

Final answer: D