Chapter 16 - Electric Potential, Energy, and Capacitance - Learning Path Questions and Exercises - Multiple Choice Questions - Page 590: 23

(d) the charge increases.

The voltage across the capacitor will remain constant as it is connected to voltage source. As dielectric is placed opposite charge will get induced on its surface which will create electric field opposite to initial electric field due to charged plate. As voltage is constant, charge on capacitor plate will increase.