Right option is (d) In no case the two duplicated genes both undergo change
To explain I would say: In a possibility, two duplicated genes both undergo change, but interactions between the proteins stabilize the original function and support the evolution of new ones. Through mutation and natural selection, one of the copies can develop a new function, leaving the other copy to cover for the original function. However, because most mutations are deleterious to function, often one of the copies becomes a pseudogene. Not all gene duplications are thought to have the above effects.