Which kind of object is the best standard candle for measuring distances to extremely distant galaxies?

Answer;

white dwarf supernovae

Explanation;A white dwarf supernovae is caused by carbon fusion starting, the carbon fuses all at once causing an explosion. A white dwarf supernovae happens when an object with very little hydrogen in its outer layer collapses so, there is little or no hydrogen absorption in the spectrum.A massive star supernovae typically has a fair amount of hydrogen left in its envelope, or at least in its immediate surroundings.White dwarf supernovae is used as a standard candle. By comparing the known luminosity of the standard candles to its observed brightness, the distance to the object can be computed using universe-square law.