Final answer:
a. Analgesic. The term that refers to a substance or mechanism that has pain-relieving properties is analgesic.
Step-by-step explanation:
The term that refers to a substance or mechanism that has pain-relieving properties is analgesic. Analgesics are drugs that reduce or relieve pain without causing loss of consciousness. They work by blocking the transmission of pain signals to the brain or by altering the brain's perception of pain. For example, common analgesics include acetaminophen (such as Tylenol) and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (such as Advil) and naproxen (such as Aleve).