听力原文：M: I would like to make a reservation for a flight to Las Vegas for March 8th.
W: Sorry, but all flights to Las Vegas are fully booked on March 8th. Actually, our flights to Las Vegas are all booked up through May 12th. It' s the spring break season, you know. There are some business class seats available for the morning of March 9th.
M: That' s too bad. Could you put my name on the waiting list on both March 8th and 9th？ I have to attend a conference in the afternoon of March 9th. By the way, how much is the business class？
W: $320 dollars, sir. It' s twice as expensive as an economy seat.
When was the man originally planning to leave for Las Vegas？

A. On March 8th
B. On March 9th
C. On March 10th
D. On March 12th