s-plane

Which one of the following statements is NOT TRUE for a continuous time causal and stable LTI system?

For the equation, $${s^3} - 4{s^2} + s + 6 = 0$$ the number of roots in the left half of $$s$$ plane will be

None of the poles of a linear control system lie in the right half of $$s$$-plane. For a bounded input, the output of this system

Closed loop stability implies that $$\left[ {1 + G\left( s \right)H\left( s \right)} \right]$$ has only ____________ in the left half of the $$s$$-plane.

Which of the following figure(s) represent valid root loci in the $$s$$ - plane for positive $$K?$$ Assume that the system has transfer function with real coefficient.