Answer:
Changing the customer number on a record in the Orders table to a number that does not match a customer number in the customer table would violate referential integrity.
If deletes do not cascade, deleting a customer that has orders would violate referential integrity.
If deletes cascade, customer can be deleted and all orders for that customer will automatically be deleted.
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C. OS hardening.
Making an operating system more secure. It often requires numerous actions such as configuring system and network components properly, deleting unused files and applying the latest patches.
The purpose of system hardening is to eliminate as many security risks as possible. This is typically done by removing all non-essential software programs and utilities from the computer.