When working with delimited flat files, is it possible to enforce primary key on a flat file using a CKM?

When working with delimited flat files, is it possible to enforce primary key on a flat file using
a CKM?

A.
No, it is not possible to enforce constraints on some technologies such as flat files and
JMS queues.

B.
No, it is not possible to enforce constraints on any technology.

C.
Yes, it is possible also to forward-engineer it to the flat file definition.

D.
Yes, but you have to save it as a fixed file.

Explanation: