A water droplet of mass m and charge q is placed between two parallel plates with a downward electric field. The droplet is negatively charged. When a certain potential difference is applied, it creates an electric field of strength E, keeping the droplet stationary. Find an equation for the droplet's charge q, given the electric field E and the droplet's weight mg.

• A. q = mE/g
• B. q = gE/m
• C. q = mgE
• D. q = mg/E