What notable difference does a custom portlet service have that is compatible with earlier
versions of IBM WebSphere Portal?

A.
Legacy services are stored in the session, and standard services are stored in the application
object.

B.
The services are retrieved differently depending on the type of portlet in use.

C.
Standard portlet services are synchronized, but IBM Portlet API services are not synchronized.

D.
Standard portlet services are synchronized, but IBM Portlet API services are not synchronized.