The scenario that describes mitosis in action is:
A skin cell repairing itself after a cut.
Mitosis is the process by which a eukaryotic cell divides its nucleus and genetic material to produce two daughter cells, typically for growth and healing purposes, such as in the case of skin cells repairing a cut. The other scenarios involve processes like fertilization (sperm and egg fusion), binary fission in bacteria (which is a form of asexual reproduction) and cellular processes not directly related to mitosis.