6. Which of the following statements are true? 
(A) Given the characteristic equation 3s2+ 5s+k = 0 of a linear control system, increasing the value of k will decrease the frequency of oscillation of the system.
(B)

can be approximated by

since the pole at -20 is much largerthan the dominant poles at O and -1.
(C) For a stable open-loop system with a perfect model P(s), it is always possible to have a stable and causalfeedforward controller F(s) such that P(s)F(s) = 1.
(D) The maximum overshoot of

 is possibly exceed 100 percent when

and Tare all positive.
(E) If a unity-feedback control system type is 2, then it is certain that the steady-state error of the systemto a step or a ramp input will be zero.