I think it’s a or b but Im confused with the question
Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).
He needed to understand the concept of science to understand why it’s so important
Answer:
The substance is DNA and it would be found in the nucleus.
Explanation:
As people go older, they would lose some of their ability to sythesize vitamin d. Also, elderly who are home bound are less likely to go outside to exercise so they do not expose the sunlight often, causing them to have lesser vitamin d