What is the difference between Virtual Circuit and Datagram?

• A. The quality of service is easy in Virtual Circuit while it is difficult in Datagram.
• B. In the connection oriented service, a connection is called as Virtual Circuit while in the connectionless service, the independent packets are called
• C. The services are independent in Virtual Circuit but that won't be so in Datagrams.
• D. Both a and b
• E. Both b and c