An alien just landed on earth (and somehow speaks English)

An alien just landed on earth (and somehow speaks English). The alien does not understand what stress is and claims to have never experienced it.  explain what stress is to the alien. Explain why and when people experience stress. Explain the human stress response to the alien including which parts of the (human) brain and nervous system are involved. Perhaps these systems have not evolved in the alien species. The alien is confused and doesn't understand why humans would have evolved such a response. Give at least one explanation for why we (humans) have evolved a stress response and why stress might be beneficial under certain circumstances.