What type of question allows participants to add more information if they choose?

The correct answer is open question because this type of question is designed to allow participants the freedom to express their thoughts, opinions, or experiences in their own words. This is particularly valuable in research settings, as it can yield rich, qualitative data that may provide deeper insights into the participants' perspectives. Open questions encourage elaboration and can reveal information that the researcher may not have anticipated, enhancing the depth and quality of the data collected.

In contrast, closed questions restrict responses to predefined options or simple yes/no answers, limiting the participant's ability to share additional information. Multiple choice questions also provide a set of fixed responses from which participants must choose, while rank order questions ask participants to rank items in a specified order without offering space for additional comments. Both of these formats can miss important nuances that open questions are adept at capturing.