The primary reason that massive O-type stars are not found in the galactic halo is that they are
a) too massive to be kicked into the halo from the disk
b) so massive that they settle into the inner disk
c) too short-lived to have persisted from halo formation until today
d) closer to us in the disk than in the extended halo
Answer: c) too short-lived to have persisted from halo formation until today