Which WAN service utilizes two different encapsulation types (one for data and one for signaling) on its data link layer?（）

A. The destination is a host on another subnet, so the router will not forward the packet.
B. The destination is a host on the same subnet, so the router will forward the packet.
C. The destination is a broadcast address, so the router will not forward the packet.
D. The destination is a network address, so the router will forward the packet.

A. It ensures that data is retransmitted if an acknowledgment is not received.
B. It reassembles segments in the correct order on the destination device.
C. It provides a mechanism for the receiver to control the transmission speed.
D. It regulates the size of each datagram segment.
E. All of the above are functions of flow control