单项选择题

W: Good morning, Sir. Could I ask you to register, please
M: Of course. What shall I do
W: Just fill in this form, if you would, please.
M: Ok, please give me a pen.

What is the relationship of the two people()

A. Salesperson and customer.
B. Doctor and patient.
C. Receptionist and tourist.
D. Lawyer and client.