The graph below shows the position versus clock readings of two trains running on parallel tracks.<br>
<img src="two_trains.jpg"
  Which of the following statements is true? <br>
<br>

(a)At time t<sub>b</sub> both trains have the same velocity. (A=true; B= false) <br>
(b) Both trains speed up all the time. (A=true; B= false) <br>
(c) Both trains have the same velocity at some clock reading before t<sub>b</sub>. (A=true; B= false)<br>
(d) Somewhere on the graph, both trains have the same acceleration.(A=true; B= false)