According to the spec, page 136,
In the case of a one-to-many relationship, if a collection of entity objects is assigned from a cmr-field of in one instance to a cmr-field of the same relationship type in another instance, the objects in the collection are effectively moved. The contents of the collection of the target instance are replaced with the contents of the collection of the source instance, but the identity of the collection object containing the
instances in the relationship does not change.
In my understanding, the target instance collection is replaced, salesrep1 contains customer2 only (not the customer 1). If it is correct, then option a is correct and what is the another option. Am I going crazy?