how are service definitions continued on the next line?

In the main Postfix configuration file, how are service definitions continued on the next line?

A.
It isn’t possible. The service definition must fit on one line.

B.
The initial line must end with a backslash character (\).

C.
The following line must begin with a plus character (+).

D.
The following line must begin with white space indentation.

E.
The service definition continues on the following lines until all of the required fields are
specified.