13. The characteristic equation of a unity-feedback control system is given by s 3 þ K1 s 2 þ s þ K2 ¼ 0: Consider the following statements in this regard: 1. For a given value of K1, all the root-locus branches will terminate at infinity for K2 in the positive direction. 2. For a given value of K2, all the root-locus branches will terminate at infinity for the variable K1 in the positive direction. 3. For a given value of K2, only one root-locus branch will terminate at infinity for the variable K1 in the positive direction. Of these statements: (a) 1 and 2 are correct (b) 3 alone is correct (c) 2 alone is correct (d) 1 and 3 are correct