—Good morning. Room Reservations. May I help you, sir?

—Yes, I’d like to book a room.

—            Which date would that be?

A．Thank you, sir.

B．That’s all right, sir.

C．You are welcome, sir.

D．No trouble,sir.

      caused the accident is still a complete mystery.

A．What

B．That

C．How

D．Where