The correct answer is option 'C', Model layer.

Explanation:
The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a communication system into seven different layers. Each layer is responsible for a specific set of tasks and protocols, allowing for the seamless transmission of data between different network devices.

However, the Model layer is not present in the OSI model. This is because the OSI model consists of the following seven layers:

1. Physical Layer: This is the lowest layer of the OSI model and deals with the transmission of raw bit streams over a physical medium. It defines the electrical, mechanical, and functional properties of the physical interface between devices.

2. Data Link Layer: This layer provides reliable transfer of data across a physical link. It is responsible for framing, error detection, and flow control. It also manages access to the physical medium.

3. Network Layer: The network layer is responsible for the delivery of data packets from the source to the destination across multiple network devices. It handles routing, addressing, and fragmentation of data.

4. Transport Layer: This layer ensures reliable end-to-end communication between the source and destination. It provides error control, flow control, and segmentation of data.

5. Session Layer: The session layer establishes, manages, and terminates sessions between applications. It provides synchronization, checkpointing, and recovery services.

6. Presentation Layer: This layer is responsible for the transformation, encryption, and compression of data. It ensures that data from the application layer is presented in a format that the application can understand.

7. Application Layer: The application layer is the highest layer in the OSI model. It interacts directly with the end-user and provides services such as file transfer, email, and remote login.

The Model layer mentioned in option 'C' is not a part of the OSI model. It may be a term used in a different context or framework, but it is not one of the recognized layers in the OSI model.