[多选题]39、 When configuring external group policies, which of the following are valid server types to use? (Choose all that apply.)当配置外部组策略时，下面哪一个是有效的服务器的类型?(选择所有满足条件的答案。)
A. RADIUS
B. TACACS+
C. LDAP
D. Windows domain controller Windows域控制器