**Core Concept**
Galton's system refers to a method of describing the location of the iris color in the eye, which involves categorizing the color into four quadrants. This system is used to predict the inheritance of eye color in offspring.

**Why the Correct Answer is Right**
Galton's system is based on the idea that the color of the iris is determined by the interaction of multiple genes, each contributing to the production of different pigments. The system categorizes the eye color into four quadrants: central, superonasal, inferonasal, and superotemporal. By analyzing the color of each quadrant, it is possible to predict the likelihood of certain eye colors being inherited. This system was first proposed by Francis Galton, a British scientist who studied the genetics of eye color.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because Galton's system does not involve the measurement of pupil size or the shape of the iris.
**Option B:** This is incorrect because Galton's system is not used for predicting the inheritance of other traits, such as height or skin color.
**Option C:** This is incorrect because the Efron's classification system is used to describe the shape of the iris, not the location of the iris color.

**Clinical Pearl / High-Yield Fact**
It's worth noting that Galton's system is a simplified model and does not take into account the complexity of eye color inheritance, which is influenced by multiple genes and environmental factors.

**Correct Answer: D. Galton's system is used for categorizing the location of the iris color in the eye.**