**Core Concept**
Calcification of teeth is a complex process involving the coordinated action of various cells, tissues, and hormones. The process of calcification is crucial for the formation of a hard, calcified structure that supports the tooth's function and longevity.

**Why the Correct Answer is Right**
The correct answer refers to the process of calcification in teeth, which typically occurs in a specific pattern. The calcification of teeth begins with the formation of the dental papilla, followed by the deposition of minerals such as calcium and phosphate. This process is regulated by various hormones, including parathyroid hormone (PTH) and vitamin D. The calcification of primary teeth, except for the third molars, is usually completed by the time the child is 3-4 years old. This is because the primary teeth have a shorter root development period compared to permanent teeth.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the type of teeth or the timing of calcification.
* **Option B:** This option is incorrect because it does not accurately describe the pattern of calcification in teeth.
* **Option C:** This option is incorrect because it does not provide a clear explanation of the calcification process in teeth.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the calcification of primary teeth is generally completed by the time the child is 3-4 years old, whereas the calcification of permanent teeth, except for the third molars, is usually completed by the time the child is 12-14 years old.

**Correct Answer:** A.