Write an equation of a line that passes through the point $\left(3,-4\right)$ and is parallel to the line $x+2y+18=0$.

• A. $y+4=-\frac12\left(x-3\right)$
• B. $y+4=-2\left(x-3\right)$
• C. $y=-\frac12\left(x-3\right)$
• D. $y-3=-\frac12\left(x+4\right)$