Answer:
B.Exactly 150 miles/hour
Explanation:
We are given that
Velocity of ball with respect to train,

Velocity of train=

We have to find the velocity of baseball travelling with respect to ground.
Velocity of ball with respect to train=Velocity of ball with respect to ground-Velocity of train
Velocity of ball with respect to ground=Velocity of ball with respect to train+Velocity of train
Substitute the values
Velocity of ball with respect to ground=100+50
Velocity of ball with respect to ground=150 miles/hour
Hence,option B is true.
B.Exactly 150 miles/hour