The time dependence of a physical quantity \(p\) is given by \(p=p_{0} \exp \left(-a t^{2}\right)\), where \(a\) is a constant and \(t\) is the time. The constant a
(a) is dimensionless
(b) has dimensions \(\left[\mathrm{T}^{-2}\right]\)
(c) has dimensions \(\left[\mathrm{T}^{2}\right]\)
(d) has dimensions of \(p\)