Determine whether the polynomials below can be the denominator of a causal stable filter:

(a) \(z^{5}+2 z^{4}+z^{3}+2 z^{2}+z+0.5\)

(b) \(z^{6}-z^{5}+z^{4}+2 z^{3}+z^{2}+z+0.25\)

(c) \(z^{4}+0.5 z^{3}-2 z^{2}+1.75 z+0.5\).