What Is the Main Argument in Favor of Expanding Banking

What is the main argument in favor of expanding banking powers into insurance and securities underwriting?

A) There is no need of regulatory monitoring of banks as the discipline of the market will regulate them.
B) It will be easier to monitor and limit the bank risk taking behavior.
C) It can enhance the banks' charter values, and it is very difficult to separate these activities in practice.
D) It can reduce the tension and conflict of interest between the investment and commercial banks.
E) There is no need to maintain a capital standard which allows banks to be more competitive.