What two changes, made independently, will enable the code to compile?

Given: What two changes, made independently, will enable the code to compile?

A.
Change the signature of Account to: public class Account.

B.
Change the signature of CheckingAccount to: public abstract CheckingAccount

C.
Implement private methods for deposit and withdraw in CheckingAccount.

D.
Implement public methods for deposit and withdraw in CheckingAccount.

E.
Change Signature of checkingAccount to: CheckingAccount implements Account.

F.
Make Account an interface.