Two equal positive charges $$+Q$$ each lie on the y axis at $$(0,a)$$ and $$(0,-a)$$. The electric field strength $$E$$ at a point $$(x,0)$$ satisfies

A

$$E=\frac{1}{4\pi\epsilon_0}\frac{2Qx}{(x^2+a^2)^{3/2}}$$

B

for large values of $$x$$, i.e. $$x\gg a$$, the electric field $$E\propto1/x^2$$

C

for $$x\ge0$$, $$E$$ is maximum at $$x=a/\sqrt2$$

D

for $$x\ge0$$, $$E$$ is maximum at $$x=0$$ and is equal to $$\frac{1}{4\pi\epsilon_0}\frac{2Q}{a^2}$$