If the matrix $$\begin{bmatrix}7 & 1 & -3 \\4 & 2 & x\\1 & -1 & 5 \end{bmatrix}$$ is singular, then x =

A

$$\frac{17}{2}$$

B

$$\frac{-17}{2}$$

C

$$\frac{19}{2}$$

D

$$\frac{-19}{2}$$