【单选题】About the desciption of VSI, which one is right?
A.
VSI is used to measure and indicate the indicated airspeed.
B.
VSI is used to measure and indicate the vertical speed when aircraft climb or descend, and it is also used to confirm whether the aircraft is keeping level flight.
C.
VSI is used to measure and indicate the true airspeed.
D.
VSI is used to measure and indicate the indicated airspeed and true airspeed.