Cross tolerance can develop between:

Cross tolerance refers to a phenomenon where tolerance to one substance results in tolerance to another substance that has similar pharmacological effects. The correct answer highlights that natural and synthetic opiates can lead to cross tolerance due to their shared action on the same receptors in the brain, specifically the opioid receptors.

Both natural opiates, such as morphine and codeine, and synthetic opiates, like fentanyl and oxycodone, interact similarly with the body's opioid system. When a person develops a tolerance to one type of opiate, their body may similarly adapt to another type, thereby reducing its effects even if it is a different form.

The other options do not accurately capture the typical relationships associated with cross tolerance. Opioids and stimulants operate on different neurotransmitter systems; CNS depressants and stimulants also don't share the same mechanisms of action, leading to separate tolerances; and while alcohol and cannabis interact in the central nervous system, they do not demonstrate cross tolerance in the same way as opiates do.