**Core Concept**
The question is testing the concept of intellectual quotient (IQ), a score derived from standardized tests designed to measure human intelligence. IQ scores are used to compare an individual's cognitive abilities to those of a large sample of the general population, with the average score set at 100.

**Why the Correct Answer is Right**
IQ scores are standardized to have a mean of 100 and a standard deviation of 15. This means that the average person's IQ score is 100, which corresponds to the mean of the distribution. The IQ score is calculated based on the performance in various cognitive tasks, such as verbal comprehension, visual-spatial skills, and working memory. The Stanford-Binet Intelligence Scale and the Wechsler Adult Intelligence Scale (WAIS) are two commonly used tests for assessing IQ.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because IQ scores are not normally distributed, but rather follow a skewed distribution, with more people scoring around the mean and fewer people scoring at the extremes.
**Option B:** This option is incorrect because IQ scores are not age-dependent, but rather measure cognitive abilities relative to the population mean.
**Option C:** This option is incorrect because IQ scores are not directly related to educational attainment, although there may be a correlation between the two.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that IQ scores are not the sole determinant of an individual's cognitive abilities or potential. Other factors such as motivation, education, and access to resources can also significantly impact cognitive development and achievement.

**Correct Answer: D. 100**