Which of the following is an example of single sign-on?

A.
An administrator manages multiple platforms with the same username and hardware token.
The same username and token is used across all the platforms.

B.
Multiple applications have been integrated with a centralized LDAP directory for authentication
and authorization. A user has to authenticate each time the user accesses an application.

C.
A password is synchronized between multiple platforms and the user is required to authenticate
with the same password across each platform.

D.
A web access control infrastructure performs authentication and passes attributes in a HTTP
header to multiple applications.