What distinguishes a medical device from a drug?

A medical device is distinct from a drug primarily in its intended use and the way it achieves its effect. Medical devices are designed to serve a medical purpose by performing a function, such as diagnosis, prevention, or treatment, but they do so without a chemical action. In contrast, drugs are substances that are intended to diagnose, cure, mitigate, treat, or prevent diseases and typically exert their effects through chemical action on the body.

B is the correct answer because it succinctly captures this difference: drugs are primarily aimed at diagnosing or preventing diseases through chemical intervention, while medical devices are employed for a broader range of applications involving physical means, like monitoring, support, or enhancement of physiological functions.

The other options are misleading or inaccurate in the context of distinguishing features. While regulatory frameworks vary, it is not universally true that devices are more regulated than drugs; the level of regulation often depends on the specific product and its risk classification. Devices do not usually contain active pharmaceutical ingredients—this characteristic is specific to drugs. Lastly, while many drugs require a prescription, there are numerous over-the-counter drugs available that can be obtained without a prescription, which does not serve as a distinguishing factor.