What is the default DN of the container where users and groups are stored?

When configuring a UNIX client to authenticate against a Microsoft Active Directory server, the top-level entry in the domain is dc=ad,dc=example,dc=com.
What is the default DN of the container where users and groups are stored?

A.
CN=USERS,DC=DA,DC=EXAMPLE,DC=COM

B.
CN=EXAMPLE,DC=AD,DC=USERS,DC=COM

C.
CN=USERS,DC=AD,DC=EXAMPLE,DC=COM

D.
CN=USERS,DC=AD,DC=EXAMPLE,DC=ORG