In the context of prototyping during the design phase of the systems development life cycle (sdlc), a prototype shows users how a particular task that was not technically feasible or appears to be unfeasible can be done.
a. requirements-based
b. phased-in-phased-out
c. computer-aided
d. proof-of-concept

d. proof-of-concept

Explanation:

Literally , a proof of concept is meant to determine the feasibility of the idea or to verify that the idea will function as envisioned. It is an exercise in which work is focused on determining whether an idea can be turned into a reality.  Its focus is to test whether the idea is viable, by giving those involved in the proof-of-concept exercise the opportunity to explore the idea's potential to be developed or built.

it can either be 2. or 4. : ) tell me if i'm wrong or right

they really not common the os x is just a better version of the os like in iphone theirs xr and their xs