Question

the light given off by an electric discharge through sodium vapor is

a continuous spectrum

of a single wavelength

an emission spectrum

white light

Explanation:

When an electric discharge passes through sodium vapor, sodium atoms emit light at specific wavelengths. A continuous spectrum (like white light from a hot object) has all wavelengths. Sodium vapor doesn't emit a single wavelength (it has characteristic lines). White light is a continuous spectrum of many wavelengths. An emission spectrum is produced when atoms emit light at specific discrete wavelengths. Sodium vapor gives an emission spectrum.

Answer:

an emission spectrum