Final answer:
The train's deceleration is -20 m/s².
Step-by-step explanation:
The deceleration of the train can be calculated using the formula:
Acceleration = (Final Velocity - Initial Velocity) / Time
Given that the initial velocity of the train is 50 m/s, the final velocity is 30 m/s, and the time taken is 10 seconds, we can substitute these values into the formula:
Acceleration = (30 m/s - 50 m/s) / 10 s
Acceleration = -20 m/s²
Therefore, the deceleration of the train is -20 m/s² (option D).