Assertion : Grafting is not usually possible in monocots.
Reasons : Sucessfule grafting requires that cambia of both stock and scion fuse to form new vascular tissues.

Options

A. If both Assertion and Reasons are true and the Reason is a correct explanatin of the Assertion.
B. If both Assertion and Reasons are true but Reason is a correct explanatin of the Assertion.
C. If Assertion is true but the Reasons is false.
D. If both Assertion and Reasons are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that "grafting is not usually possible in monocots." This means that when we try to graft plants that belong to the monocot group (like grasses, lilies, etc.), it generally does not work.

2. **Understanding Grafting**: Grafting is a horticultural technique where a part of one plant (the scion) is joined with another plant (the rootstock) so that they grow together as one plant. This is commonly used for propagating plants and improving their characteristics.

3. **Role of Vascular Cambium**: For grafting to be successful, the vascular cambium of both the scion and the rootstock must fuse together. The vascular cambium is a layer of tissue that produces new vascular tissues (xylem and phloem) which are essential for the transport of water, nutrients, and food within the plant.

4. **Monocots vs. Dicots**: In dicots (plants with two cotyledons), the vascular cambium is present, allowing successful grafting. However, in monocots, the vascular cambium is absent. This absence is the primary reason why grafting is not successful in monocots.

5. **Evaluating the Reason**: The reason states that "successful grafting requires that cambia of both stock and scion fuse to form new vascular tissues." This is indeed true and supports the assertion that grafting is not possible in monocots due to the lack of cambium.

6. **Conclusion**: Both the assertion and reason are true. The reason correctly explains why grafting is not possible in monocots.

### Final Answer:
Both the assertion and reason are true, and the reason is a correct explanation of the assertion.