Vamos analisar as alternativas:
a) Cd(z) = 7,55z−8 / 2,06z−3
b) Cd(z) = 0,9765z−0,4082 / z+0,3906
c) Cd(z) = 402 / (0,05 * 3z−8) / (8z+9)
d) Cd(z) = 2,6z−0,3973 / 1,0596z−0,3444
e) Cd(z) = 2,6z−3 / 7,55z−8
A alternativa correta é a letra e) Cd(z) = 2,6z−3 / 7,55z−8.