A particle's position relative to time

[candycooke]

The position y of a particle moving along the y-axis depends on the time t according to
the equation y = at - bt2. The dimensions of the quantities a and b are respectively:
A. L2/T, L3/T2
B. L/T2, L2/T
C. L/T, L/T2
D. L3/T, T2/L
E. none of these

I don't understand what the question is asking, nor do I understand what the variables in the answers represent. Any help making sense of the question and answers is greatly appreciated.

 

[Kurdt]

Its basically the kinematic equation for position. In the kinematic equation a and b are represented by physical quantities which have units. What are the dimensions of those physical quantities.