The Routh-Hurwitz criterion cannot be applied when the characteristic equation of the system contains any coefficients which is :
(a) Negative real and exponential function
(b) Negative real, both exponential and sinusoidal function of s
(c) Both exponential and sinusoidal function of s
(d) Complex, both exponential and sinusoidal function of s
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My query is from Stability Analysis topic in section Digital Control Systems of Control Systems