In the Lighthouse Model

In the Lighthouse model:

A) pulsars are observable only if they lie in the galactic plane.
B) pulsars are navigational devices created by interstellar navigators as discovered by Jocelyn Bell in 1967.
C) all pulsars have their poles pointed directly at us or they would be not observable.
D) if the beams sweeps across us, we can observe the pulse.
E) the period of pulsation must speed up as the neutron star continues contracting.