Which most likely appear in the central nervous system only? sensory neurons interneurons motor neurons effector neurons

Interneurons.

Explanation:

"Interneurons (also known as association neurons) are neurons that are found exclusively in the central nervous system. That means that they are found in the brain and spinal cord and not in the peripheral segments of the nervous system." - Google.

abueno

Explanation:adios master B)

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).