What is the term for the layers of bony matrix surrounding the vessels and nerve?

Explanation:

Each osteon consists of lamellae, layers of compact matrix surround a central canal (the haversian or osteonic canal) which contains the bone's blood vessels and the nerve Fibre. Osteon in compact bone tissue are aligned in the same direction along lines of stress, helping the bone resist bending or fracturing.

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the answer would be 3

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).