Answer:
The correct answer would be meristem.
Meristem refers to the plant tissue which consists of undifferentiated cells.
These cells can divide and differentiate to form different structures of the plant.
These cells divide and help in the growth of the plant.
They are mainly of three types: apical, intercalary, and lateral meristem.
Apical meristem helps in the vertical growth of the plant whereas the lateral meristem helps in the lateral growth, that is, growth girth or diameter of the plant.