Hardly anything ______ more than the happiness of seeing someone using his device for treatment.

I’d like to go with you.[B] No problem.[C] Sorry. I’m busy now. Go away.[D] Of course. Go down this street and turn left.

A．Sorry, the number is engaged. Will you hold on
B．Yes, speaking.
C．Hello. Who are you, please
D．Hello. Thank you for calling.