$ax^{3}+bx^{2}+cx+d$ is a polynomial on real $x$ over real coefficients $a,b,c,d$ wherein $a\neq 0$. Which of the following statements is true?
1.  $d$  can be chosen to ensure that  $x= 0$ is a root for any given set  $a,b,c$
3.  $a,b,c,d$ can be chosen to ensure that all roots are complex
4.  $c$ alone cannot ensure that all roots are real