Final answer:
The IFC beat frequency used to treat chronic pain is commonly in the range of 80-150 pps, which helps penetrate deeper tissues for pain relief.
Step-by-step explanation:
The IFC beat frequency commonly used to treat chronic pain is option c, which is in the range of 80-150 pulses per second (pps). This range is effective for penetrating deeper tissues and providing pain relief through the interference of electrical currents at frequencies that can interact with the body's neurological system. Frequencies lower than 50 pps can sometimes be used for treating acute pain, but for chronic pain, the higher range of 80-150 pps is more common and beneficial.