Cepheid Variable Stars Are Invaluable in Astronomy Because of the Close

Multiple Choice

Cepheid variable stars are invaluable in astronomy because of the close relationship between

A) the peak wavelength of their spectra and their surface temperatures.
B) their luminosity, or absolute magnitude, and their pulsation period.
C) the redshift of their spectra and their distance from the Sun.
D) their apparent magnitude and their pulsation period.