Blood banks will shortly start to screen all donors for NANB hepatitis. Although the new screening tests are estimated to disqualify up to 5 percent of all prospective blood donors, they will still miss two-thirds of donors carrying NANB hepatitis. Therefore, about 10 percent of actual donors will still supply NANB-contaminated blood.

19. The argument above depends on which of the following assumptions?

(A) Donors carrying NANB hepatitis do not, in a large percentage of cases, carry other infections for which reliable screening tests are routinely performed.

(B) Donors carrying NANB hepatitis do not, in a large percentage of cases, develop the disease themselves at any point.

(C) The estimate of the number of donors who would be disqualified by tests for NANB hepatitis is an underestimate.

(D) The incidence of NANB hepatitis is lower among the potential blood donors than it is in the population at large.（A）

(E) The donors who will still supply NANB-contaminated blood will donate blood at the average frequency for all donors.

没看明白题中的数字关系,请帮助解释一下.谢谢!

E说带肝炎的捐献者的捐献频率和所有捐献者的平均水平一致。

取非，带肝炎的捐献者过分积极捐献，或者过分消极，都会导致结论10%得不正确。

大家觉得如何？