In May 2010, the New York Times Ethicist, Randy Cohen

In May 2010, the New York Times ethicist, Randy Cohen, described a scenario of one person donating his kidney to another person. Later, the donor experiences some financial trouble and the receiving person considers helping them out with a financial gift. Economist Greg Mankiw continues: "So what does the Ethicist say about all this? Apparently, both of these gifts are noble acts, worthy of the highest praise and admiration. Unless, that is, there is some reason to think they are linked together. In that case, the reallocation of resources (kidney, cash) would be a despicable market transaction."
Based on this information, which is the most likely explanation for the Ethicist's disapproval of selling kidneys?

A) meddlesome preferences
B) fair and equal treatment
C) cultural goods
D) distribution of income