Which is NOT a function of magnesium in the body? znutritio acting as a cofactor for enzyme systems in the Irody
regulating bone and mineral status
protecting teeth from acid-forming bacteria
making up one component in bone mineral

I think it is the third one which states, "Protecting teeth from acid-forming bacteria".

Explanation:

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.