What explains why individuals with the same genotype can show different phenotypes (variable expressivity)?

What explains why individuals with the same genotype can show different phenotypes (variable expressivity)?

• A. Expressivity depends only on genotype
• B. Variation in gene expression due to modifiers, environment, or epistasis leads to different expressivity
• C. Expressivity is constant across individuals
• D. Expressivity is due to random mutation

Answer: (B)