Transport Layer is the correct answer.

The Transport Layer is responsible for linking the network support layers and user support layers. It provides end-to-end communication between the source and destination hosts. Let's understand why the other options are not correct:

a) Application Layer: The Application Layer is responsible for providing services directly to the end users. It includes protocols such as HTTP, FTP, SMTP, etc. This layer is not involved in linking the network support layers and user support layers.

c) Physical Layer: The Physical Layer is the lowest layer of the OSI model. It deals with the physical transmission of data over the network. It includes specifications for cables, connectors, electrical signals, etc. This layer is not responsible for linking the network support layers and user support layers.

d) Data Link Layer: The Data Link Layer is responsible for node-to-node communication within a network. It deals with the framing of data, error detection, and flow control. While it is involved in the transmission of data within a network, it does not link the network support layers and user support layers.

e) Network Layer: The Network Layer is responsible for routing packets from the source to the destination network. It includes protocols such as IP, ICMP, ARP, etc. While it plays a crucial role in network communication, it does not directly link the network support layers and user support layers.

In summary, the Transport Layer is the correct answer as it is specifically designed to link the network support layers (Network Layer, Data Link Layer, and Physical Layer) with the user support layers (Application Layer). It ensures reliable and efficient delivery of data between hosts.