48. A specific locus in a large, sexually reproducing deer mouse population is analyzed. Researchers find that the locus exhibits high nucleotide variability (many base-pair differences across individuals) but extremely low gene variability (less than1% heterozygosity). Assuming this population is large and mating is random, which explanation best accounts for the coexistence of these two variability measurements? (A) The high nucleotide variability is solely maintained by directional selection favoring one homozygous genotypе. (B) Genetic drift has caused the rapid fixation of the most common allele, simultaneously eliminating all new nucleotide mutations. (C) The majority of the nucleotide differences occur in noncoding regions (introns) or represent silent substitutions, resulting in few distinct functional alleles (low gene variability). (D) Balancing selection is actively maintaining two or more forms in the population, contradicting the observed low heterozygosity. (E) Gene flow is consistently introducing new alleles that are immediately selected against before they can be replicated within the population. NTHU115