Final answer:
Disassortative mating within a population is the option that is not involved in gene flow, as gene flow involves the transfer of genetic material between different populations.
Step-by-step explanation:
The option that could not be involved in gene flow is choice 3) Disassortative mating within a population. Gene flow is the transfer of genetic variation from one population to another. It is an important component in the evolutionary process and can occur through various mechanisms such as gametes dispersed by ocean currents, wind-blown pollen, zygotes dispersed by ocean currents, and hybridization between neighboring populations. Disassortative mating, however, is a mating pattern within a population where individuals with dissimilar genotypes or phenotypes tend to mate with each other, and it does not result in the transfer of genetic material between different populations.