Match the polynomial function to its correct roots

Place the letter of the list of correct roots next to each function listed below:

 1. $f(x)=x^4-18 x^2+81$
 2. $f(x)=x^4+6 x^3+18 x^2+54 x+81$
 3. $f(x)=x^4-12 x^3+54 x^2-108 x+81$
 4. $f(x)=x^4+12 x^3+54 x^2+108 x+81$

A. $x= 3$, with multiplicity 2, $x = -3$, with multiplicity 2
B. $x = 3$, with multiplicity 4
C. $x= -3$, with multiplicity 2, $x = 3i, x=-3i$
D. $x=-3$, with multiplicity 4