Final answer:
Opiate drugs bind onto the same receptor sites as the body's endorphins and relieve pain.
Step-by-step explanation:
Opiate drugs bind onto the same receptor sites as the body's own endorphins, which are natural painkillers produced by the body. This binding action allows opiate drugs to relieve pain. Therefore, the correct answer is (c) relieve pain. Opiate drugs like heroin, morphine, methadone, and codeine have analgesic properties and can be used as strong painkillers.