The correct answer is A: A technique to connect amateur radio systems, such as repeaters, via the internet using Voice Over Internet Protocol (VoIP). The Internet Radio Linking Project (IRLP) is a technique to connect amateur radio systems via the internet using VoIP. IRLP allows repeaters and other radio systems to be linked together over the internet, enabling worldwide communications. For amateur radio operators, IRLP extends the range of local repeaters by connecting them to repeaters worldwide, allowing contacts that wouldn't be possible with radio alone. Understanding IRLP helps explain how internet-linked repeaters work.