In the case of disruptive selection, the distribution curve for a trait generally shows a pattern where extreme phenotypes are favored over intermediate phenotypes. This leads to the formation of two distinct peaks in the distribution, indicating that the population is diverging into two groups. Therefore, the correct response is:
It shifts to the left and the right.
This indicates that there are increases in the frequencies of the traits at either end of the distribution while the intermediate traits tend to decrease.