Before participating in an experiment, the participants must sign a document affirming that they have been told the basic outlines of the study and are aware of what their participation will involve, what risks the experiment many hold, and the fact that their participation is purely voluntary and they may terminate it at any time. This refers to which ethical principle of research

informed consent

Explanation:

Informed consent is an ethical principle employed in research, especially a research involving clinical trials that has to deal with human subjects. This ethical principle is hinged on the legal premise that prioritize the autonomy of the subject in a research. This means, that the researcher must communicate in clear terms, to the participants or human subjects, what the experiment entails and is all about, the benefits and risks the participants are exposed to. It also stresses that the participants, having understood what is being communicated to them, should voluntarily give the researcher the express permission to carry on with the procedure on them.

The information given in the question clearly refers to the ethical principle of research known as informed content.

answer; eliminate parking problems in cities, because a car took up only half as much space as a horse and buggy;

answer; empathy;