[单选题]
A car decelerates unyfd l8,; kzq**k2clpxiforllx9- x odq/c*mly and comes to a stop after 10 s. The car's average velocity during deceleration was 50 km/h. What was/-*oclqxdx l 9 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