Correct option is C
Strut:
A structural member subjected to an axial compressive force is called strut. As per definition strut may be horizontal, inclined or even vertical. Vertical strut is called a column.
It is a web member of a roof truss or brace frame subjected to light axial compressive loads.
Column or post or stanchion:
It is a vertical member of a steel building frame that is used to support a floor girder or floor subjected to heavy axial compressive loads.
Boom:
It is a principle compression member of a crane.
