Which of the Following Constitutes an Open-Ended Invitation? ​

Which of the following constitutes an open-ended invitation? ​

A) "When we talked on the telephone you said you were having trouble with your boss. What is the problem there?"
B) "I'd like to begin by learning more about the concerns that have brought you to therapy. What has been the difficulty?"
C) "I understand you are having difficulty with you husband. What is the problem?"
D) "Your physician has referred you to me for help with your agoraphobia. How long have you had it?"