Chapter 16 - Electric Potential, Energy, and Capacitance - Learning Path Questions and Exercises - Multiple Choice Questions - Page 589: 12

(c) they are the same

The force on electron or proton will be same as both have equal charge magnitude and force is given by $Eq$, where E is the electric field due to the plate and q is the charge. The charge on both electron and proton is same in magnitude. Hence, the displacement of both electron and proton is same.