Idea: Ask which option is about managing changes to items over time.
SCM answers the question of what changed, when, and by whom. The tool and practice that records each version and lets you revert is Version Control:
\[ v_1 \to v_2 \to v_3 \to \dots \]
Design, testing and maintenance are lifecycle phases, not the change-tracking backbone. So the key SCM component is Version Control.
\[\boxed{\text{Option C: Version Control}}\]