The process of making certain that an entity (operating system, application, etc.) is as secure as it can be
known as:

A.
Stabilizing

B.
Reinforcing

C.
Hardening

D.
Toughening

Explanation:
Hardening is the process of securing a system by reducing its surface of vulnerability. Reducing the surface of
vulnerability typically includes removing unnecessary functions and features, removing unnecessary usernames
or logins and disabling unnecessary services.