11. A government agency that reimburses its clients for bills they have paid for medical care has had this year’s budget cut. To save money without cutting reimbursements or otherwise harming clients financially, it plans to delay reimbursements to clients for forty days, thereby earning $180 million per year in interest on the reimbursement money.

Which of the following, if true, is the best criticism of the agency’s plan?

(A) Hospitals and physicians typically hold patients responsible for the ultimate payment of their bills.

(B) The agency cannot save money by cutting staff because it is already understaffed.

(C) Some clients borrow money to pay their medical bills; they will pay forty extra days of interest on these loans.

(D) Some clients pay their medical bills immediately, but they often take more than forty days to file with the agency for reimbursement.

(E) The agency’s budget was cut by more than $180 million last year.

The correct answer is C, while I think D is also reasonable. If as D states, some clients often take more than forty days to file the reimbursement, it seems that the delay for reimbursement may be not effective in earning interests for the agancy (becasue clients already make the delay before this plan is adopted). Thus D can weaken agency's plan. However, I guess that there must be something wrong with my reasoning, just cannot point it our. So please nicely help!

Many thanks!