Final answer:
The behavioral effect of opioids from the provided options is euphoria, which is a profound sense of well-being that contributes to the addictive nature of these substances.
Step-by-step explanation:
The behavioral effect of opioids among the following options is C. Euphoria. Opioids are known to produce a profound sense of well-being and pleasure, which can contribute to their addictive properties. Other effects of opioids, like miosis (pinpoint pupils), are part of their physiological impacts rather than behavioral. Options such as increased arousal, diarrhea, and tachycardia are not typically associated with the immediate behavioral effects of opioids.
Addiction, dependence, and rehabilitation are critical concerns in the context of opioid use. Addiction can lead to a compulsive need to use the drug despite negative consequences, while dependence refers to the physical or psychological withdrawal symptoms experienced when stopping the drug.