Answer:
d. all of the statements are correct
Step-by-step explanation:
Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model. i.e Layers 1 and 2 They are designed to cope with bursty traffic. Frame relay is also a form of data networking based on packet switching in which the packets are variable in length and experience packet delays.
Based on the above definition the correct statement is option d as all of the statements define in the other option correctly defines the function of frame relay.