**Core Concept**
Gustafson's method is a technique used for estimating the age of a human being based on the examination of certain changes in the teeth, specifically the root resorption and the incremental lines of cementum. This method takes into account the fact that the rate of root resorption and the formation of incremental lines of cementum are relatively constant in humans.

**Why the Correct Answer is Right**
Gustafson's method involves measuring the following changes in the teeth: the length of the root, the width of the periodontal ligament space, the height of the alveolar bone, the transparency of the root, the secondary dentin formation, and the incremental lines of cementum. By analyzing these changes, the age of the individual can be estimated. The incremental lines of cementum, in particular, are formed at a relatively constant rate, making them useful for age estimation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided. Please provide the other options for a complete explanation.
**Option B:** Incorrect because Gustafson's method does not involve measuring the length of the root alone, but rather a combination of the changes mentioned above.
**Option C:** Incorrect because the transparency of the root is one of the changes measured in Gustafson's method, but it is not the only change involved.
**Option D:** Incorrect because the incremental lines of cementum are indeed a part of Gustafson's method, but the other changes mentioned above are also crucial for accurate age estimation.

**Clinical Pearl / High-Yield Fact**
Gustafson's method is a useful tool for forensic odontology, particularly in cases where the age of the individual is unknown or disputed. However, it is essential to note that this method has its limitations and should be used in conjunction with other methods of age estimation to achieve more accurate results.

**Correct Answer:** Not provided (Please provide the correct options to complete the explanation)