问一道逻辑题 实在做不出来！！

轩辕亦舒

旧prep里面的 假设题 实在是这2个选项分不清楚 麻烦高人指点！！！

Bank depositors in the United States are all financially protected against bank failure because the government insures all individuals' bank deposits.An economist argues that this insurance is partly responsible for the high rate of bank failures, since it removes from depositors any financial incentive to find out whether the bank that holds their money is secure against failure.If depositors were more selective, then banks would need to be secure in order to compete for depositors' money.

The economist's argument makes which of the following assumptions?

(D) The difference in the interest rates paid to depositors by different banks is not a significant factor in bank failures.

(E) Potential depositors are able to determine which banks are secure against failure.

答案是E
我选了D  因为我觉得就是否定了一个可能让结论成立的答案  但是我取非了觉得不一定能削弱原文 因为取非后 interest rate 是bank failure很重要的原因 并不代表government的原因不重要
但是E  我觉得如果取非的话  如果人们没有能力辨别，那就可能deposit到sucure低的bank 那么bank就会破产 但是跟government也没有关系啊？  

希望牛人指点啊 不胜感激！！！