**Core Concept:** The Wechsler Intelligence Scale for Children (WISC) and Wechsler Adult Intelligence Scale (WAIS) are standardized tests used to evaluate intelligence. They provide an IQ score based on the performance of the individual on various tasks. IQ stands for Intelligence Quotient, and the average IQ represents the average score of a normal population.

**Why the Correct Answer is Right:** The correct answer is **C. 100**. The average IQ of a normal child is derived from the scores of the entire population tested using these scales. According to the normative data, the distribution of IQ scores is approximately normally distributed, with a mean score of 100 and a standard deviation of 15. This means that about 68% of the population falls within +/- 15 points of the mean, and about 95% falls within +/- 30 points.

**Why Each Wrong Option is Incorrect:**

A. **90**: This is too low, as it falls below the range of 85-90, which is considered borderline intelligence impairment.

B. **110**: This is too high, as it exceeds the range of 115-120, which is considered superior intelligence.

D. **140**: This is also too high, as it exceeds the range of 140+, which is considered genius-level intelligence.

**Clinical Pearl:** The IQ scores obtained from these tests are often used for comparison with the individual's peers or for diagnosing intellectual disabilities or giftedness. However, it is essential to consider the whole picture of an individual's clinical presentation and not solely rely on IQ scores. Intelligence is a complex concept influenced by various factors, including cognitive abilities, environmental influences, and developmental stage.