Bank depositors in the United States - Kindly explain

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 thatholds 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.

A. Bank failures are caused when big borrowers default on loan repayments.
B. A significant proportion of depositors maintain accounts at several different banks.
C. The more a depositor has to deposit, the more careful he or she tends to be in selecting a bank.
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.

I read the explanation for this question posted earlier in the forum. However, I am unable to understand the structure of this argument. Can anyone state the conclusion, premise and how assumption fits in for this argument.

Thank you.