The potential at a point $x$ (measured in $\mu m$) due to some charges situated on the $x$-axis is given by $V(x) = \frac{20}{x^2 - 4} \text{ volt}$. The electric field $E$ at $x = 4 \mu m$ is given by:

• A
  $\frac{10}{9} \text{ V/}\mu m$ and in the $+ve \ x$ direction
• B
  $\frac{5}{3} \text{ V/}\mu m$ and in the $-ve \ x$ direction
• C
  $\frac{5}{3} \text{ V/}\mu m$ and in the $+ve \ x$ direction
• D
  $\frac{10}{9} \text{ V/}\mu m$ and in the $-ve \ x$ direction