A) The incidence of new cases of NANB hepatitis is likely to go up by 10 percent.
Relationship between donors with NANB and cases isn't given; Maybe 10 % is utilized by 2%?; Eliminate

B) Donations made by patients specifically for their own use are likely to become less frequent.
Irrelevant; Eliminate

C) The demand for blood from blood banks is likely to fluctuate more strongly.
Fluctuate means go up, down, or both. While the demand can go up due to the shortage caused by the disqualification of 5% of donors, other options can't be consequences of the new test. Eliminate.

D) The blood supplies available from blood banks are likely to go down.
Solid option, if the donors go down, then the supplies will go down. Hold.

E) The number of prospective first-time donors is likely to go up by 5 percent.
Goes too far; Eliminate.

Ans: D