As Time Progresses,the Pulse Rate for Most Solitary Pulsars Is

Multiple Choice

As time progresses,the pulse rate for most solitary pulsars is

A) slowing down because rotational energy is being used to generate the pulses.
B) absolutely constant: Pulsars provide ideal frequency standards or clocks.
C) varying periodically as the neutron star undergoes periodic expansions and contractions.
D) speeding up,as the neutron star slowly contracts under gravity.