How Might You Distinguish a Sodium-Vapor Street Lamp from a Mercury-Vapor

How might you distinguish a sodium-vapor street lamp from a mercury-vapor street lamp?

A) Use binoculars to look for printing adjacent to the bulb.
B) Look at the street lamps through a spectroscope and match their spectral patterns to their respective atomic spectra.
C) Ask your local utility company to identify these lamps for you.
D) The shadows cast from a sodium-vapor street lamp tend to be more diffuse around the edges.