Discontinuous Variation in ABO Blood Groups

Steps:

• Identify discontinuous variation as traits with distinct categories, no intermediates (e.g., A, B, AB, O blood types).
• Examine graph for discrete bars or peaks representing fixed phenotypes, not a smooth curve.
• Confirm absence of values between categories, indicating no blending.
• Match to choice describing limited, separate phenotypes.

Why B is correct:

• Discontinuous variation features a finite number of distinct phenotypes, as seen in ABO groups (4 types), per Mendelian genetics.

Why the others are wrong:

• A: Intermediate percentages would imply blending, suggesting continuous variation.
• C: A range between extremes describes continuous traits like height, not discrete blood groups.
• D: Wording is incomplete and redundant; does not clearly define discontinuity.

Final answer: B