Apical meristems are specialized regions of undifferentiated cells located specifically at the growing tips (apices) of stems and roots. They undergo continuous cell division (mitosis) to produce new cells, allowing the plant to grow in length (primary growth).

A. Intercalary meristems are found at the base of leaves and nodes, particularly in monocots like grasses. They also contribute to an increase in length (e.g., leaf regrowth after mowing), but they are located in the middle of the plant, not the apex.

C. Meristematic is the general term for any plant tissue composed of actively dividing cells. Apical, intercalary, and lateral are all types of meristematic tissue. The question asks for the specific type found at the apex.

D. Lateral meristems are found along the sides of stems and roots. They are responsible for secondary growth, which increases the plant's girth or width, not its length at the apex.