To answer this question, we need to understand the OSI (Open Systems Interconnection) model and the function of each layer.
The OSI model is a conceptual model that standardizes the functions of a communication system into seven layers. Each layer performs specific tasks and provides services to the layer above it.
Option A) Layer 7 - This layer is the Application layer, which focuses on providing network services to applications. It deals with protocols that enable user applications to access the network. It is not concerned with the transmission of unstructured bit streams.
Option B) Layer 1 - This layer is the Physical layer, which is responsible for the transmission of unstructured bit streams over a physical link. It deals with the physical medium, such as cables, connectors, and electrical signals.
Option C) Layer 6 - This layer is the Presentation layer, which is responsible for the formatting and encryption of data. It ensures that the data is in a format that the application layer can understand. It is not concerned with the transmission of unstructured bit streams.
Option D) Layer 2 - This layer is the Data Link layer, which provides error-free transfer of data frames between nodes over a physical link. While it is involved in the transmission of data, it does not handle unstructured bit streams. It deals with data frames that have a specific structure and format.
The correct answer is Option B) Layer 1. This layer, the Physical layer, is concerned with the transmission of unstructured bit streams over a physical link. It handles the physical medium and the electrical signals necessary for communication.