Sulfur trioxide is known to be planar with all the oxygen atoms equidistant from the central sulfur atom. On the basis of these facts, which of the following conclusions may be drawn concerning this molecule?
I. It can be represented by three equivalent resonance structures.
II. The dipoles associated with each SO bond are equal in magnitude.
III. The sulfur atom is sp² hybridized.

- I only
- II only
- III only
- I and II only
- I, II, and III