From an Observational Standpoint, What Is a Pulsar

Multiple Choice

From an observational standpoint, what is a pulsar?

A) A star that slowly changes its brightness, getting dimmer and then brighter, with a period of anywhere from a few hours to a few weeks.
B) An object that emits flashes of light several times per second (or even faster) , with near perfect regularity.
C) An object that emits random "pulses" of light, sometimes with only a fraction of a second between pulses and other times with several days between pulses.
D) A star that changes color rapidly, from blue to red and back again.