A fixed input is one:

A) that only exists in nature,and there is only so much of it.
B) that can be used for one thing only.
C) that can never produce more or less in any period.
D) whose quantity cannot be changed in the short run.

Fixed Input

A resource or factor of production whose quantity remains constant regardless of the level of output or activity.

Short Run

A period in economics where at least one input is fixed and cannot be changed, limiting the ability to increase production.