Read this: The vast majority of visitors in Greece in 2007 came from the European continent, numbering 12.7 million, while the most visitors from a single nationality were those from the United Kingdom, (2.6 million), followed closely by those from Germany (2.3 million). In 2010, the most visited region of Greece was that of Central Macedonia, with 18% of the country's total tourist flow (amounting to 3.6 million tourists), followed by Attica with 2.6 million and the Peloponnese with 1.8 million. Northern Greece is the country's most-visited geographical region, with 6.5 million tourists, while Central Greece is second with 6.3 million.

What is the single nation with the most visitors?
What is the answer? (If it cannot be answered, return "unanswerable")
United Kingdom