Two general divisions of drugs are

• A. Agonists and antagonists
• B. Stimulants and depressants
• C. Activators and inhibitors
• D. Carriers and modulators

Answer: (C)

Understanding how drugs work often starts with whether they boost or dampen activity at a target. Activators are agents that increase the function of a target—think of a molecule that turns a receptor on or enhances an enzyme’s activity to push a reaction forward. Inhibitors do the opposite, blocking a receptor, blocking an enzyme, or preventing a transporter from moving a substance, thereby reducing the physiological response. This activator/inhibitor framework covers a broad range of drug actions across many targets, making it a useful general way to categorize drugs.

Other pairings tend to be narrower in scope. Agonists and antagonists describe interactions at receptors specifically, which is a subset of the broader activator/inhibitor idea. Stimulants and depressants refer to overall central nervous system arousal levels, not a universal way to classify all drugs. Carriers and modulators aren’t standard broad categories for all drug actions, whereas activators and inhibitors capture the general dichotomy of increasing vs decreasing target activity.