The cambium occupy between two vascular bundles is called interfascicular cambium. It is a secondary meristem. During the secondary growth in a dicot stem, the fascicular and interfascicular cambium fuse together to form a continuous ring of meristematic tissue called the Vascular Cambium.

Fascicular, interfascicular, and extrastelar cambium together constitute:

The correct answer is option 'A', lateral meristem. Let's understand why this is the case:

Definition of cambium:
Cambium is a type of lateral meristem that is responsible for the secondary growth in plants. It is a layer of actively dividing cells located between the xylem and phloem in the stem and root of a plant.

Now, let's break down the given options and understand their meanings:

a) Lateral meristem:
Lateral meristem refers to the meristematic tissue that is responsible for the growth in diameter or girth of a plant. It includes the cambium, which is responsible for secondary growth. In this context, fascicular cambium, interfascicular cambium, and extrastelar cambium are all examples of lateral meristem.

b) Primary meristem:
Primary meristem refers to the meristematic tissue that is responsible for the primary growth of a plant, which includes the formation of the primary tissues (epidermis, ground tissue, and vascular tissue). It does not include the cambium, which is responsible for secondary growth.

c) Ground meristem:
Ground meristem refers to the meristematic tissue that gives rise to the ground tissue system of a plant. It includes the formation of parenchyma, collenchyma, and sclerenchyma cells. Ground meristem does not include the cambium, which is responsible for secondary growth.

d) Intercalary meristem:
Intercalary meristem refers to the meristematic tissue that is found at the base of leaves or internodes in grasses. It is responsible for the elongation of these structures. Intercalary meristem does not include the cambium, which is responsible for secondary growth.

Therefore, the correct answer is option 'A', lateral meristem, as fascicular, interfascicular, and extrastelar cambium are all examples of lateral meristem. They are responsible for the secondary growth of plants by adding new cells to the vascular tissues (xylem and phloem) and increasing the girth or diameter of the plant.

Cambium is secondary in origin so answer is lateral meristem