"Standard Candles," Which Are Important for Finding Distances to Remote

Multiple Choice

"Standard candles," which are important for finding distances to remote galaxies,are

A) standard laboratory light sources with which the brightness of a galaxy can be compared.
B) heat sources used for calibrating infrared observations of galaxies.
C) stars and other objects of known intrinsic brightness.
D) laboratory light sources with a well-known spectrum for calibration of stellar and galactic spectra.