The characteristic equation of a closed-loop automatic control system in time domain is given by

\[ D^{5}+2 D^{4}+4 D^{2}+D+1=0 \]

Consider the following statements in this regard:

1). The system is linear 2). The system is non-linear 3). The system is stable 4). The system is unstable Of these statements

(a) 1 and 3 are correct

(b) 2 and 3 are correct

(c) 1 and 4 are correct

(d) 2 and 4 are correct.