Beyond the answers - interesting background to this quiz

Baku and the language of "-stan"

Azerbaijan's capital, Baku, sits on the western shore of the Caspian Sea, the largest inland body of water in the world. The name Azerbaijan is often linked to the Persian words for "guardian of fire", a nod to the natural gas fires that have burned on the Absheron peninsula for centuries. The wider region is full of place names ending in "-stan", a Persian suffix meaning "land of", which also appears in the names of countries such as Kazakhstan, Uzbekistan and Afghanistan.

The periodic table's hidden logic

Radium's symbol, Ra, follows a neat convention: most chemical symbols simply take the first letter of the element's name, sometimes adding a second letter for clarity. That is why radium is Ra, radon is Rn and ruthenium is Ru. Radium was once used in glow-in-the-dark watch dials before its health dangers became clear, and it sits in the same group of the periodic table as calcium, which is why the body can mistake it for that mineral.

Country codes and where they come from

Vehicle registration codes are not always the obvious abbreviation. Sweden's plate code is simply S, while Switzerland uses CH, from Confoederatio Helvetica, its Latin name. Codes are assigned internationally to avoid confusion, and some countries have changed theirs over time as new nations appear. Next time you spot a foreign plate, the letters often tell a small story about a country's history or official language.

Chad, at the crossroads of Africa

Chad takes its name from Lake Chad, a shallow body of water that has shrunk dramatically over recent decades and is shared with Niger, Nigeria and Cameroon. The country borders Libya to the north, Sudan to the east and Niger to the west, placing it at the meeting point of the Sahara and the Sahel. Its capital, N'Djamena, lies close to the Cameroonian border, and the country's landscape ranges from desert in the north to savanna in the south.