Which command is useful when troubleshooting AAA Authentication between a Cisco router and the AAA server?

Which command is useful when troubleshooting AAA Authentication between a Cisco router and
the AAA server?

A.
test aaa-server test cisco cisco123 all new-code

B.
test aaa group7 tacacs+ auth cisco123 new-code

C.
test aaa group tacacs+ cisco cisco123 new-code

D.
test aaa-server tacacs+ group7 cisco cisco123 new-code

Explanation: