Answer:
a. as corporations.
Explanation:
Local governments cannot establish banks. Therefore, option B is the wrong answer.
A bank cannot be a credit union. It is a member-owned cooperative business that shares profit. Therefore, option C is not the answer.
The only central bank is established to fulfill the reserve requirement. Hence, option D is incorrect.
Banks are established by the help of institutional investors or shareholders' equity. Therefore, most banks are established as a corporation. So, option A is the answer.