A linear time-invariant system initially at rest, when subjected to a unit-step input gives a response \(y(t)=t e^{-t} ; t>0\). The transfer function of the system is
(a) \(\frac{1}{(s+1)^{2}}\)
(b) \(\frac{1}{s(s+1)^{2}}\)
(c) \(\frac{s}{(s+1)^{2}}\)
(d) \(\frac{1}{s(s+1)}\)