"a female peacock is checking out the potential mates" - males with excellent plumage displays. when she sees a male with vibrant colors, shiny feathers, and a confident stride - these are likely examples of what?

Intersexual selection

Sexual selection is a process in which an organism survival and reproduction is favored by it's phenotypic traits. The one organism having better phenotypic trait will be able to attract members of opposite sex in order to copulate and reproduce new organism. Here, the attractive feathers in male peacock is a useful phenotypic trait to attract female mates is an example of intersexual selection.

a and c are the answeres