A__________is a type of active galaxy nucleus that is especially variable and has few or no spectral emission lines.
A) blazar
B) pulsar
C) quasar
D) quark
Question 2
In the context of measuring the properties of galaxies, a__________is an object of known brightness that astronomers use to find distance.
A) black hole
B) white dwarf
C) standard candle
D) red giant