On which Open System Interconnection (OSI) Reference Model layer are repeaters used as
communications transfer devices?

A.
Data-link

B.
Physical

C.
Network

D.
Transport

Explanation:
This original answer is wrong (network) repeater is physical layer. Repeaters just
regenerates the signal
“Hubs are multi port repeaters, and as such they obey the same rules as repeaters (See previous
section OSI Operating Layer). They operate at the OSI Model Physical Layer.”
http://www.thelinuxreview.com/howto/intro_to_networking/c5434.htm