The graph shows position as a function of time for 2 trains running on parallel tracks.

Question

The graph shows line A at a 45 degree angle,beginning at origin.
Curve B also begins at origin, continues up and to the right (all in quadrant 1, like a sq root function) It crosses Line A at T sub b.

Which is true?
a. both trains have the same velocity.
b. both trains speed up all the time.
c. both trains never have the same velocity
d. the trains never have the same acceleration.

How do I figure this out by looking at the graph? Thank you.