What are the two common terms used to describe traffic signal supports and signal heads?

Answer: C — Rigid and free-swinging

The two common terms used to describe traffic signal supports and signal heads are indeed "rigid" and "free-swinging." Rigid supports refer to structures that are fixed and do not move or sway significantly in response to external forces. These are designed to hold traffic signal heads in a stable position, ensuring that the signals are visible and operational under various environmental conditions. On the other hand, free-swinging supports allow a certain degree of movement. This can be beneficial in certain conditions, such as when high winds are present, as it enables the signal to pivot slightly instead of risking damage or dislodgment. Understanding these terms is crucial for traffic signal technicians as it impacts the installation and maintenance of traffic signals, ensuring they function correctly and safely monitor and guide traffic flow.