Beyond the answers - interesting background to this quiz

A river that refuses to belong to one country

The Mekong begins on the Tibetan Plateau and runs roughly 4,300 kilometres through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before emptying into the South China Sea. Laos is the country in our quiz, but the river is a lifeline for tens of millions of people across the whole region, supplying fish, irrigation and transport. Its lower stretches support one of the world's most productive inland fisheries.

Why Mars looks red

Mars owes its distinctive colour to iron oxide - essentially rust - in its soil and dust. That same dust often swirls into planet-wide storms. The planet is also home to Olympus Mons, the tallest known volcano in the solar system, and Valles Marineris, a canyon system that dwarfs anything on Earth. Its two small moons, Phobos and Deimos, are named after figures from Greek mythology.

From pulp fiction to a literary landmark

Kurt Vonnegut drew on his own experience as an American prisoner of war in Dresden during the Second World War when writing Slaughterhouse-Five. The novel blends science fiction, memoir and dark satire, following the soldier Billy Pilgrim as he becomes "unstuck in time". Published in 1969 during the Vietnam War, it became one of the defining anti-war novels of the twentieth century.

The palla and the Roman wardrobe

The palla was a draped outer garment worn by women in ancient Rome, usually wrapped over a tunic and often fastened at the shoulder with a brooch. Made from wool or linen, it could be pulled up over the head as a veil in public. Together with the stola, the long dress associated with respectable married women, it formed the backbone of female Roman dress.

Gutenberg and the machine that changed reading

Johannes Gutenberg did not invent printing from scratch - woodblock printing already existed in East Asia - but his fifteenth-century press combined movable metal type, oil-based ink and a screw press adapted from wine-making. The result was faster, cheaper reproduction of texts, beginning with his famous Bible. Printing spread rapidly across Europe and helped fuel the Renaissance and the Reformation.