🔍 Key Concepts

• Simplex vs. duplex operation in marine VHF communications • Role of the International Telecommunication Union (ITU) in standardizing frequencies • Meaning of frequency pairs in radio communication

💭 Think About

• Ask yourself: does a duplex channel usually use one frequency or two for communication between ship and shore? • Think about what the ITU does: does it focus on one country (like the U.S.) or international standards? • Which choice best reflects a formal, global system for organizing how VHF channels are used?

✅ Before You Answer

• Verify whether duplex means using separate transmit and receive frequencies. • Confirm that ITU work products are typically international, not U.S.-only. • Check which option clearly mentions a pair of frequencies and common (shared) use.