Which two statements about HDLC are true? (Choose two)
A it resides on the network layer
B It is incompatible with full-duplex links
C The physical layer clocks and synchronizes communication between links
D Its frames are non-synchronous
E It can insert an delete bits in the frame to prevent the delimiter flag's bit pattern from appearing within data fields.
I think the answer is C,E, but many docs show D,E ?
