Why is the electric field between ideal large parallel plates often treated as uniform?

• A. Because conducting plates eliminate all charge variation in the region between them, forcing $\overrightarrow{E}$ to vanish
• B. Because the potential difference is zero between equipotential surfaces
• C. Because Gauss's law requires the field inside any capacitor to be constant everywhere
• D. Because the plate separation is small compared with plate dimensions, field lines are nearly parallel and the magnitude is approximately constant away from edges

Answer: (D)