If an operating system does not allow a child process to continue after its…

Concept: Processes can form a parent-child hierarchy. An operating system may apply a termination policy to that hierarchy when a process ends.

Under a propagating policy, ending one process triggers termination of its descendants, so the effect travels down the process tree.

Application: The stem says that a child is not allowed to continue after its parent terminates. This is precisely cascading termination.

Contrast: The other terms refer to different process concepts:

• Threading describes multiple execution threads within a single process that share its resources.

• A zombie is a completed child whose process-table entry remains until its parent collects the exit status.

• Process killing is a general act of terminating a process and does not by itself name a hierarchy-wide policy.

Cross-check and result: If the terminated parent has children and grandchildren, the policy removes them down the hierarchy. Therefore, the phenomenon is cascading termination.