A.10e-10t B.e-10t C.0.1e-0.1t D.e-0.1t
A.3/(s+2) B.3/(s+0.5) C.6/(s+2) D.6/(s+0.5)
A.k-ke-1/Tt B.k-e-1/Tt C.k-ke-Tt D.k-e-Tt