At which layer of the OSI model does error checking occur with IPv6?（）

A. SONET and SDH both use time-division multiplexing.
B. An optical transport network system uses time-division multiplexing.
C. SONET and SDH both use wavelength-division multiplexing.
D. An optical transport network system uses wavelength-division multiplexing.

A. The receiver acknowledges the final packet in each communications stream.
B. The receiver adds sequencing numbers to the packets received.
C. The sender adds sequencing numbers to the packets it sends.
D. The receiver acknowledges each packet it receives from the sending device.

A. packet segmentation
B. serialized checking
C. packet sequencing
D. parallel checking