听力原文：Can I have your attention, please？ Passengers waiting for flight GE sixty-four, t

here's been a gate change. Let me repeat that: Flight GE sixty-four, flying to Charlotte and then on to Miami, is NOT departing from Gate F-twenty-seven. Flight GE sixty-four will depart from Gate B-nine. The departure time has been pushed back from four o'clock to four-fifteen. A shuttle to concourse B will be arriving shortly. We're sorry for the inconvenience, but the plane that is currently here at Gate F-twenty-seven is experiencing mechanical troubles and will not be going anywhere for a while. So we'll be taking off from Gate B-nine instead. Thank you for your patience.

What is the purpose of this announcement？

A．To announce the arrival of a flight

B．To notify passengers of a gate change

C．To advise travelers about a new security procedure

D．To let passengers know where their baggage will arrive