Although their responsibilities vary from country to country, central banks' duties (and the justification for their existence) usually fall into three areas : （ ）
选项：

A:Manage checking deposits for individuals
B:control and manipulate the national money supply
C:regulate member banks through capital requirements, reserve requirements, and deposit guarantees, among other tools
D:acts as an emergency lender to distressed commercial banks and other institutions, and sometimes even a government