Final answer:
A pipe wrench should be used to tighten PVC and CPVC pipe flange joints.
Step-by-step explanation:
The correct answer is A) Pipe.
When tightening PVC and CPVC pipe flange joints, it is recommended to use a pipe wrench. A pipe wrench provides a secure grip and mechanical advantage to apply torque and tighten the joints. This helps ensure that the joints are properly sealed and prevent leakage.