Help with homwork - Astronomy We might expect to not find life around halo stars (“Population II” stars) because:

a)
they are out of the plane of the galaxy and thus exposed to more cosmic rays (energetic
nuclei)

b)
these stars are all too hot and thus will expose any planets to too much ultraviolet radiation

c)
these stars lack the heavy elements (“metals”) out of which life can form

d)
these stars have existed too short a time for life to have evolved

e)
the stars all pass too close to the central supermassive black hole in the Milky Way

I am stumped on this question, any ideas?
You will need to find out what population II 
 stars are.

When you understand what a population II star is, ask yourself two questions about each statement:

For example a) "Are population II stars out of the plane of the galaxy, and do they receive more cosmic rays", and "Would receiving more cosmic rays actually prevent life from forming". If you can answer yes to both questions, you have a potential answer.

If you judge that several answers are possible, then re-read the definition of a population II star, and ask which statement is most pertinent to the definition of such a star. Good luck.