Normal distribution of polygenic traits

Steps:

• Examine the diagram's graph shape, showing a symmetric bell curve.
• Identify it as a continuous distribution with most values clustering around the mean.
• Recall that polygenic traits, influenced by multiple genes and environment, produce such normal distributions.
• Compare options: only height fits as a continuous, normally distributed trait.

Why C is correct:

• Height is a polygenic trait governed by multiple genes, resulting in a normal distribution per the central limit theorem for additive genetic effects.

Why the others are wrong:

• A. Blood group: discrete categories (A, B, AB, O) form a bar graph, not continuous.
• B. Eye colour: discrete phenotypes (e.g., blue, brown) yield categorical distribution.
• D. Sex: bimodal distribution (male/female) at roughly 50% each, not bell-shaped.

Final answer: C