Solution

A - X.25 is connection‐oriented network: True

• X.25 is an International Telecommunications Union - T standard protocol suite for packet-switched data communication in wide area networks.
• It usually allows various logical channels to make use of same physical line and hence, it is a connection-oriented network.

B - X.25 doesn’t support switched virtual circuits: False

• X.25 is an International Telecommunications Union - T standard protocol suite for packet-switched data communication in wide area networks.
• It supports switched virtual circuits and permanent circuits.​

C - Frame relay service provides acknowledgements: False

• Frame Relay is a packet switching technology that fragments packets into transmission units called frames and send it at high-speed through a digital network.
• It establishes an exclusive connection during the transmission period called virtual connection. In frame relay network, there are no acknowledgements sent from the switches back to the sender.

D - Frame relay service provides detection of transmission errors: True

• Frame Relay is a packet switching technology that fragments packets into transmission units called frames and send it at high-speed through a digital network. 
• The frame relay network will detect errors with the frame's FCS, discarding any frames found to be in error.