A proton travels into the uniform electric field between two parallel vertical metal plates in a vacuum. One plate is held at $0\,\text{V}$ and the other at $+10\,\text{V}$, as shown. What immediate change does the electric field produce in the proton’s motion straight after it enters the field?
- AIt begins to move downwards.
- BIt begins to move upwards.
- CIts speed decreases.
- DIts speed increases.