The correct answer is: C. DECT
DECT (Digital Enhanced Cordless Telecommunications) is a digital cordless telephone system that was first developed in the 1980s. It is a widely used standard in Europe and Asia, and is also approved as a 3G standard.
PHS (Personal Handy-phone System) is a digital cordless telephone system that was developed in Japan in the 1990s. It is a popular standard in Japan, but is not widely used in other parts of the world.
PACS (Personal Access Communications System) is a digital cordless telephone system that was developed in the United States in the 1990s. It is not a widely used standard.
CT2 (Cordless Telephone 2) is a digital cordless telephone system that was developed in the United Kingdom in the 1980s. It is not a widely used standard.
DECT is a more advanced standard than PHS, PACS, and CT2. It offers higher quality voice and data transmission, and is more reliable. DECT is also more secure than PHS, PACS, and CT2.
DECT is a good choice for businesses and homes that need a reliable and secure cordless telephone system.