In a vector electric-field map, what does a longer arrow at one location indicate compared with a shorter arrow at another location, assuming both arrows point in the same direction?
a) Field lines are closer together at the location with the longer arrow, but the electric-field magnitude is the same at both locations.
b) The electric potential is higher at the location with the longer arrow, while the electric-field magnitude is unchanged.
c) The electric-field magnitude is greater at the location with the longer arrow.
d) The charge producing the field is larger at the location where the arrow is longer.