The characteristic equation of a control system is given by s6+2s5+8s4+12s3+20s2+16s+16=0 . The number of the roots of the equation which lie on the imaginary axis of s-plane:

The characteristic equation of a control system is given by s6+2s5+8s4

1.	The characteristic equation of a control system is given by s6+2s5+8s4+12s3+20s2+16s+16=0 . The number of the roots of the equation which lie on the imaginary axis of s-plane:
A.	t0
B.	t2
C.	t4
D.	t6
Answer» D. t6