The root locus of unity feedback system is shown in figure

The closed loop transfer function of the system is

In the formation of Routh-Hurwitz array for a polynomial, all the elements of a row have zero values. This premature termination of the array indicates the presence of

A cascade of three identical modulo -$$5$$ counters has an over all modulus of

Which of the following logic circuits is a realization of the function $$F$$ whose karnaugh map is shown in figure