Answer :
D. Open-ended questions.
Open-ended questions do not constrain clients to limited response options, instead, they encourage clients to express themselves more fully, providing richer, more nuanced information. This fosters a more in-depth conversation and helps the therapist to better understand the client's experiences and feelings. On the other hand, closed-ended questions, which often result in yes or no answers, limit the depth of response and may not be as useful in a therapeutic context where understanding the nuances of a client's experience is crucial. Dichotomous questions fall under the category of closed-ended questions and also restrict responses to two options, which may be too limiting when dealing with complex human emotions. Therefore, when therapists seek to create a dialogue that encourages clients to explore their thoughts and feelings in detail, open-ended questions are the most suitable choice.