Answer:a
Explanation:
Introducing a dielectric inside a capacitor reduces the Electric field . Charge develops on dielectric such that it is opposite to the corresponding face . For example Positive charge of capacitor induces negative charge on dielectric which will create an Electric Field in opposite direction.
So Electric Field decreased by a factor of [tex]\frac{1}{K}[/tex] where
[tex]K=dielectric\ magnitude[/tex]