[单选题]
A car decelerates unicc0 jazt edvzf36d8.9 fo eghzw0 cvwl(be8+14y rmly and comes to a stop after 10 s. The car's average vel(whzg8 c4lveeb+wy1 0ocity during deceleration was 50 km/h. What was the car's deceleration while slowing down?
A. 10 km/h/s
B. 5 km/h/s
C. 250 km/h/s
D. 10 km/h/s