[单选题]
A car decelerates unifoo:v: poh vn0g.rmly and comes to a stop afterceo0 p/qxr or,ep/5 2x 10 s. The car's average velocitoqc 2 e/pr0oxer, x5p/y 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