If an operating system does not allow a child process to exist when the parent process has been terminated, this phenomenon is called:

Explanation

Many operating systems enforce that no child process may continue to exist once its parent has terminated; when the parent exits, the OS recursively terminates all of its children (and their children, and so on) rather than orphaning them. This standard OS textbook term for the chain-reaction is cascading termination, option (ii). 'Zombie' refers to a different situation — a child that has finished but whose exit status has not yet been collected by its parent — so 'zombie termination' and the other two options describe unrelated concepts.