A force defined by F=α t^2+β t acts on a particle at a given time t. The factor which is dimensionless, if α and β are constants, is:

A force defined by $\displaystyle F=\alpha t^2+\beta t$ acts on a particle at a given time $\displaystyle t$. The factor which is dimensionless, if $\displaystyle \alpha$ and $\displaystyle \beta$ are constants, is: