Beyond the answers - interesting background to this quiz

The gas we rarely think about

Nitrogen makes up roughly 78 percent of the air around us, with oxygen a distant second at about 21 percent. Despite its abundance, nitrogen is chemically unreactive under normal conditions, which is why it does not fuel fires or react with most materials. It becomes useful to life only when certain bacteria, or industrial processes, convert it into compounds that plants can absorb.

A two-term limit written into law

Barack Obama served eight years as US president, from 2009 to 2017, winning re-election in 2012. American presidents are limited to two elected terms by the 22nd Amendment to the Constitution, ratified in 1951. The rule was a response to Franklin D. Roosevelt, who had won four elections, and it has shaped every presidency since.

A capital that rose from the ashes

Podgorica is the capital of Montenegro, a small country on the Adriatic coast that declared independence in 2006. The city was largely destroyed during the Second World War and rebuilt in a distinctly modern style. Tirana, one of the other options, is the capital of neighbouring Albania, while Skopje belongs to North Macedonia.

Gershwin's bridge between two worlds

George Gershwin composed "Rhapsody in Blue", first performed in 1924 with the Paul Whiteman orchestra in New York. The piece blends classical structure with jazz rhythms and blues-inflected melodies, helping to establish a distinctly American concert sound. Gershwin went on to write the opera "Porgy and Bess" before his early death in 1937.

The river that roars

The Zambezi forms the border between Zimbabwe and Zambia and is the fourth-longest river in Africa. Along its course it plunges over Victoria Falls, known locally as Mosi-oa-Tunya, or "the smoke that thunders". The river then flows through Mozambique before emptying into the Indian Ocean.