A train of length l, travelingat a constant velocity, passes a pole in ... ...

A train of length l, traveling at a constant velocity, passes a pole in t seconds. If the same train traveling at the same velocity passes a platform in 3t seconds, then the length of the platform is
(A)        0.5l
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Press: Set S - Word Problems