Under Most Models for the Preservation of Duplicated Genes That

Under most models for the preservation of duplicated genes that eventually perform new functions,what is the proposed order of events and evolutionary reasoning behind them?

A) After a gene is duplicated, it must rise to high frequency in a population due to drift; only after it has risen to high frequency will it then be likely to evolve to perform a new function favored by natural selection.
B) After a gene is duplicated, one of the copies must evolve to perform a new function that increases an organism's fitness; only after the new function evolves will the duplicated gene rise in frequency within the population due to natural selection.
C) After a gene is duplicated, it will typically be favored by natural selection even before it evolves to perform a new function, because having duplicate gene copies provides beneficial redundancy within genomes. Therefore, duplicate copies rise to high frequency in a population due to natural selection, and later a new function can evolve that is also favored by natural selection.
D) Duplicated genes usually differ in function immediately after duplication, because gene duplication is an imperfect process and mutations are typically introduced during duplication. If the duplicate copy happens to perform a new function that benefits an organism, it rises in frequency in the population due to natural selection.