$I.$ Energy stored in ${C_1}$ $=$ Energy stored in ${C_2}$ $+$ Energy stored in ${C_3}$
$II.$ Charge on ${C_1}$ $=$ Charge on ${C_2}$ $+$ Charge on ${C_3}$
$III.$ Potential drop across ${C_1}$ $=$ Potential drop across ${C_2}$ $=$ Potential drop across ${C_3}$
Which of these is/are correct
$(A)$ the electrostatic field is zero
$(B)$ the electrostatic potential is constant
$(C)$ the electrostatic field is constant in magnitude
$(D)$ the electrostatic field has same direction
$\varepsilon(x)=\varepsilon_{0}+k x, \text { for }\left(0\,<\,x \leq \frac{d}{2}\right)$
$\varepsilon(x)=\varepsilon_{0}+k(d-x)$, for $\left(\frac{d}{2} \leq x \leq d\right)$

