Introduction:
In a multimaster system, multiple devices or nodes are interconnected to share data and resources. To ensure accurate and efficient communication between these nodes, specific ports are used. These ports facilitate the exchange of information and help avoid errors.

Explanation:
The correct answer is option 'B', bidirectional port. Let's understand why this is the case:

Bidirectional Port:
- A bidirectional port is capable of transmitting and receiving data in both directions simultaneously.
- In a multimaster system, bidirectional ports are used to establish communication between multiple nodes.
- These ports allow for the exchange of data and commands between nodes, enabling them to work together seamlessly.
- Bidirectional ports ensure that each node can send and receive information without conflicts or errors.

Unidirectional Port:
- Unidirectional ports only allow data transmission in one direction.
- In a multimaster system, using unidirectional ports can lead to communication issues and errors.
- If a node can only transmit data and not receive it, it may miss important commands or updates from other nodes, resulting in synchronization problems.

Multi-directional Port:
- Multi-directional ports do not exist in the context of a multimaster system.
- The term "multi-directional" may be a misnomer or a misinterpretation of bidirectional ports.
- The use of multi-directional ports in a multimaster system would not provide the necessary bidirectional communication required for effective coordination among nodes.

Tridirectional Port:
- Tridirectional ports do not exist in the context of computer networking or communication protocols.
- The term "tridirectional" is not commonly used or recognized in the field.
- Using tridirectional ports in a multimaster system would be an unconventional approach and may lead to compatibility issues and errors.

Conclusion:
The correct port used in a multimaster system to avoid errors is a bidirectional port. It allows for simultaneous data transmission and reception, ensuring effective communication and coordination among multiple nodes. Unidirectional, multi-directional, and tridirectional ports are not suitable for this purpose and may result in communication errors and synchronization problems.