Final answer:
The oldest drug produced by humans is alcohol, with evidence of its production and use dating back to ancient times, potentially over 10,000 years ago.
Step-by-step explanation:
The oldest drug produced by humans, according to the textbook, is alcohol (c). Historical evidence suggests that the production of alcohol dates back to ancient times and has been part of human civilization for thousands of years, potentially more than 10,000 years. In comparison to other psychoactive substances listed like marijuana, opium, and caffeine, alcohol is believed to have been produced and consumed by various cultures across different continents long before the others became widely used.