Extinction only happens above the species level cannot happen to more than one species at a time has happened to over 99% of species that ever lived on earth happens when a species or population dies out

The extinction is a process that occurs when an specific species no longer exists. It can occur by natural events (earthquake, Ice ages) or human influence (pollution, hunting, industrial production). So, the answer is: "happens when a species or population dies out).

The answer will be d