Why Are We Unlikely to Find Earth-Like Planets Around Halo

Multiple Choice

Why are we unlikely to find Earth-like planets around halo stars in the Galaxy?

A) Planets around stars are known to be extremely rare.
B) Halo stars formed in an environment where there were few heavy elements to create rocky planets.
C) Any such planets would have been ejected long ago by galactic mergers.
D) Halo stars do not have enough mass to hold onto planets.
E) Halo stars formed in a different way from disk stars.