Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. when this occurs, it is possible for genes from bird flu virus and human flu virus to be combined, thereby producing a genetically distinctive virus, which can subsequently cause widespread disease. the production of new types of flu virus in the manner described above is most similar to the phenomenon of

This question is incomplete as the following options should have been provided: 
A) bottleneck effect. 
B) founder effect. 
C) natural selection. 
D) gene flow. 
E) sexual selection.

The correct answer is D: gene flow. Gene flow is the transfer of genetic variation from one population to another. If there is sufficiently high genetic transfer between two populations, they can be considered one population. Gene flow is important for transferring genetic diversity between populations, and the movement between populations can change allele frequencies. Of relevance to this example, new variants may result from the exchange of genetic material between the populations.