Beyond the answers - interesting background to this quiz

The element that barely exists

Francium, symbol Fr, sits at the bottom of the alkali metals group, but you will never find it on a shelf. It is one of the rarest elements in the Earth's crust, and every known isotope is radioactive with a very short half-life. Even a visible sample would instantly decay, which is why chemists study it only through traces produced in laboratories.

Babbage, Turing and the many fathers of computing

Charles Babbage designed the Analytical Engine in the 19th century, a mechanical machine that anticipated the basic structure of modern computers, with a processor and memory. Ada Lovelace wrote notes describing how it might handle far more than numbers, which is why she is often called the first programmer. Alan Turing came later, formalising computation and breaking codes during the Second World War. The "father of computing" title depends on which chapter of the story you value most.

The boy raised by wolves

Mowgli first appeared in Rudyard Kipling's 1894 collection The Jungle Book, a set of stories set in the Indian jungle. Kipling wrote them while living in Vermont, drawing on his childhood in India and on folk tales he had heard there. The character has since been reinvented countless times, from Disney's animated musical to darker film adaptations, but the original Mowgli is a quieter, more ambiguous figure than most screen versions suggest.

A capital that was rebuilt from rubble

Warsaw became Poland's capital in 1596, when King Sigismund III moved his court there from Krakow. During the Second World War the city was almost completely destroyed, and its historic centre was reconstructed in the decades that followed. That reconstruction was later added to UNESCO's World Heritage list, a rare recognition of a painstakingly rebuilt old town.

The Kremlin: fortress before residence

The Kremlin in Moscow began as a fortified settlement, and its walls and towers have been rebuilt many times over the centuries. It served as a royal residence, a religious centre and later the seat of Soviet government. Today it is the official residence of the Russian president, and its cathedrals and palaces sit alongside administrative buildings inside the red-brick walls.