The apex is located at the
a. cementoenamel junction.
b. cervical neck.
c. tip of the root.
d. apical foramen.

The correct answer is option C. "tip of the root".

Explanation:

According to botanical terminology, the apex also known as the apical root meristem is a small region located at the tip of the root. The apex is comprised of cells capable of replenish dying cells and perform repeated division to keep the plant growing. The root apex allows the development of the root hair structures, which facilitate water and mineral absorption.