Power in external resistor from circuit current

Steps:

• Total resistance is R + r.
• Current I = E / (R + r).
• Power P in R is I²R.
• Substitute: P = E²R / (R + r)².

Why B is correct:

• B does not match; correct power uses R in numerator, not ER/r.

Why the others are wrong:

• A: Incorrect units and form; mixes voltage with resistance ratio improperly.
• C: Swaps R and r in standard formula, giving power in internal resistance divided by r.
• D: Gives power dissipated in internal resistance r, not external R.

Not enough information for given options, as none match standard formula. Final answer: \frac{E^2 R}{(R + r)^2}