Which advantage of using questionnaires is highlighted in terms of ethical issues?

The highlighted advantage of using questionnaires in the context of ethical issues is that participants can leave questions unanswered. This feature is crucial because it respects the participant's autonomy and sensitivity to certain topics. Ethical research practices prioritize informed consent and the well-being of participants. By allowing individuals to skip questions, researchers minimize the risk of causing discomfort or distress, particularly regarding personal or sensitive issues. Participants having the option to omit questions enhances their sense of control over their involvement in the research, ultimately contributing to a more ethically sound research environment.

In contrast, the other options do not emphasize ethical considerations to the same extent. Building rapport (the second option) is important for qualitative research, aiming for deeper engagement, but it may not directly pertain to ethical issues like the ability to leave questions unanswered does. Ensuring that all questions are answered (the third option) focuses more on data completeness rather than ethical concerns. Conducting questionnaires in a one-on-one setting (the fourth option) can facilitate better understanding, but it is the flexibility in answering that directly addresses participants' rights and ethical standards.