Which protocol is used to resolve a known IP address to an unknown
MAC address?

A.
ICMP

B.
RARP

C.
ARP

D.
TFTP

Explanation:
The Address Resolution Protocol (ARP) sends a broadcast asking
for the host with a specified IP address to reply with its MAC, or
hardware address. This information is kept in the ARP Cache.
* the Reverse Address Resolution Protocol (RARP) is
commonly used on diskless machines, when the MAC is known, but
not the IP address. It asks a RARP server to provide a valid IP
address, which is somewhat the reverse of ARP.
* the Internet Control Message Protocol (ICMP) is a management protocol
for IP.
* the Trivial File Transfer Protocol (TFTP), is a stripped-down version of the File Transfer Protocol
(FTP).

Source:
CCNA Study Guide by Todd Lammle, Donald Porter, and James
Chellis (Sybex, 1999).