The correct answer is: C. the gainers can compensate the losers for their loss and still remain better-off themselves than before.
The Kaldor-Hicks compensation criterion is a potential Pareto improvement criterion. It states that a change in economic policy is considered to be an improvement if the gainers from the change could compensate the losers and still be better off than before, even if the losers do not actually receive compensation.
Option A is incorrect because it does not require that the gainers be better off after compensating the losers. Option B is incorrect because it does not require that the gainers be able to compensate the losers. Option D is incorrect because it does not require that the gainers be better off after the change.