Introduction:
A knuckle joint is a type of mechanical joint that allows angular movement between two rods or pipes. It consists of a spherical ball and a socket, which are connected by a cylindrical pin. The maximum number of roads that can be connected using a knuckle joint depends on the design and construction of the joint.

Explanation:
The knuckle joint allows angular movement between the connected rods or pipes. However, it has limitations in terms of the number of roads that can be connected. Let's analyze the options provided in the question:

Option A: 2 roads
If only two roads are connected using a knuckle joint, it forms a simple hinge joint. In this case, there is no angular movement between the rods or pipes.

Option B: 3 roads
When three roads are connected using a knuckle joint, it forms a T-joint. In this configuration, the central road is connected to the other two roads, allowing angular movement between them.

Option C: 4 roads
If four roads are connected using a knuckle joint, it forms a cross-joint. In this case, the central road is connected to the other three roads, allowing angular movement between them.

Option D: 5 roads
Connecting five roads using a knuckle joint is not possible. The joint design and construction do not allow for the necessary angular movement between all the connected roads.

Conclusion:
Based on the analysis, the correct answer is option B, which states that a maximum of three roads may be connected using a knuckle joint.