$$x^4 - 4x^3 + 6x^2 - 4x + 1 = 0$$(x ≠ 0) $$\Rightarrow x + \frac{1}{x} =$$

A

$$\frac{1}{2}$$

B

$$2$$

C

$$\frac{5}{2}$$

D

$$\frac{3}{2}$$