The Oldest Stars in the Galaxy Are Usually __________ in Heavy

The oldest stars in the galaxy are usually __________ in heavy elements because __________.

A) low; they have had time to accrete unprocessed gas from the interstellar medium
B) low; they were formed before much chemical enrichment had taken place
C) low; old stars must have low mass, and low-mass stars do not generate many heavy elements
D) high; they have turned a lot of their initial hydrogen and helium into heavier elements
E) high; stars with higher fractions of heavy elements have shorter lifetimes