Beyond the answers - interesting background to this quiz

When a currency disappears from everyday use

The guilder was the Netherlands' currency for centuries before the country adopted the euro in 2002, so older Dutch price tags and banknotes still carry a familiar name that has since faded from daily life. The krone, meanwhile, survives in several northern European countries, a reminder that the continent never settled on a single money. Currency questions like this one often hinge on knowing which countries joined the euro and which chose to keep their own.

An island in the world's largest ocean

Taiwan sits in the Pacific, the planet's biggest and deepest ocean, which stretches from the Arctic edge down to the Southern Ocean. Its position off the southeastern coast of China places it along one of the busiest shipping and trading routes in the world. That location has shaped the island's history, economy and culture far more than any single border ever could.

A moon that hints at an ocean

Europa is one of Jupiter's many moons, and it is among the most studied objects in the solar system. Beneath its icy shell, scientists believe a salty ocean may exist, which is why missions have been planned to study it up close. Its name comes from Greek mythology, where Europa was a Phoenician princess, a fitting link for a moon orbiting a planet named after a god.

Mountains that cross a border

The Appalachian Mountains run along the eastern side of North America, stretching from the southern United States up into Canada. That range explains why two separate questions in this quiz can both point to the same mountain chain: it is not confined to one country. The Appalachians are also among the oldest mountain ranges on Earth, worn down over hundreds of millions of years into the gentler slopes seen today.