Figure shows a capacitor having three layers between its plates. Layer x is vacuum, y is conductor, and z is a dielectric. Which of the following change(s) will result in increase in capacitance?

$C=\frac{A{\epsilon }_0}{\left(\frac{t_1}{K_1}+\frac{t_2}{K_2}+\frac{t_3}{K_3}\right)}$
If any one or more of the  $K$ value(s) is/are increased, the capacitance increases. $K$ of a conductor is infinity 
Replace x by conductor -  $K$ increases Option (A) is correct
Replace y by dielectric -   $K$ decreases Option (B) is wrong
Replace z by conductor -  $K$ increases Option (C) is correct
Replace x by dielectric -  $K$ increases Option (D) is correct