The Reason Type Ia Supernovae Are Useful to Astronomers for Determining

The reason type Ia supernovae are useful to astronomers for determining distances to other galaxies is that

A) they only occur in spiral galaxies, for which no other way of getting distances is available
B) it is easy to measure the blueshift produced by such explosions
C) they are much larger than many other objects that can be seen in galaxies
D) they are very bright, and generally reach the same peak luminosity
E) they produce very energetic pulsars whose radio radiation can be detected across vast distances