A unit vector perpendicular to the vectors $$\overrightarrow{a} = 2i - 3j + k$$ and $$\overrightarrow{b} = i + j - 2k,$$ is

A

$$\frac {1}{\sqrt 3} (-i + j + k)$$

B

$$\frac {1}{\sqrt 3} (i + j - k)$$

C

$$\frac {1}{\sqrt 3} (i + j + k)$$

D

$$(i + j + k)$$