Answer: surface.
- A surface
- B single point
- C straight line
- D point charge
Correct answer: A. surface
Explanation: Flux counts the field lines threading a given surface.
Field lines always point from positive to negative charge, are denser where the field is stronger, and never cross; an isolated positive charge has lines radiating symmetrically outward, while a dipole's lines curve from the positive to the negative charge.
Concept context
Coulomb's law, electric field, potential, capacitors, Gauss's law.