Please explain

Answer choice (D) is describing an ad hominem attack, when the argument does not make an ad hominem attack. Proposal: Allow individuals to setup savings accounts in which interest earned would be exempt from taxes until money is withdrawn from the account. Why? Its implementation would increase the amount of money available for banks to loan at a relatively small cost to the government in lost tax revenues. The author criticizes this proposal by explaining that when similar inventive programs were attempted in the past, most of the money invested through them was diverted from other personal savings and the overall level of personal savings was unchanged. So, the author is not criticizing the JUDGMENT OF THE PROPOSAL'S BACKERS. The actual backers of the proposal are never mentioned, nor are they criticized. Rather, the author brings up previous examples of programs similar to the proposal at hand that did not work well because they ended up not changing the overall level of personal savings. Thus, the author challenges the premise that proposal is based on, since the proposal is believed to increase the amount of money available fro banks to loan. Hope that helps! Please let us know if you have any other questions.