According to federal regulations, human subjects are defined as living individuals from whom researchers collect information through:

The definition of human subjects in the context of federal regulations involves living individuals who are the source of data collection through a variety of means, particularly through interaction or intervention by the researcher. The key aspect here is that the research must involve direct engagement, which encompasses both communication and intervention. This means that researchers are not only gathering responses but may also be influencing or altering conditions for the subjects involved in the study, thereby impacting their wellbeing or their behavior.

By focusing on communication and intervention, the regulatory definition clearly delineates the types of interactions researchers must consider when conducting studies involving human subjects. This focus on direct human interaction is essential for ethical oversight and ensuring participants' rights and welfare are protected throughout the research process.

Other response choices, such as observation only, surveys and polls, and document analysis, do not fully encompass the regulatory definition because they either pertain to passive data collection techniques or do not imply a direct interaction with the subjects being studied. Thus, they do not align with the broader, more interactive scope of what constitutes research involving human subjects as per federal regulations.