When talking about the physical elements of the Internet, the term redundancy refers to:

A) transmitting multiple copies of a single packet to safeguard against data loss.
B) the use of tiered high-speed switching computers to connect the backbone to regional and local networks.
C) delays in messages caused by the uneven flow of information through the network.
D) multiple duplicate devices and paths in a network built so that data can be rerouted if a breakdown occurs.

D