Beyond the answers - interesting background to this quiz

The river that refuses to stay in one country

The Mekong begins on the Tibetan Plateau and travels through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before emptying into the South China Sea. Its lower basin supports one of the world's richest inland fisheries, and the river's seasonal flood pulse is what makes that abundance possible. Because so many countries depend on it, the Mekong is also a constant subject of diplomatic negotiation over dams, water sharing and navigation.

A novel that grew out of a small-town childhood

Harper Lee drew on her own upbringing in Monroeville, Alabama, when she wrote To Kill a Mockingbird, published in 1960. The story of Scout Finch and her father Atticus, a lawyer defending a Black man falsely accused, won the Pulitzer Prize for Fiction in 1961. It remains one of the most widely taught American novels, and its depiction of racial injustice in the Depression-era South still fuels classroom discussion.

The Alamo: a mission first, a battlefield second

The Alamo in San Antonio was originally a Spanish mission before it became a fortress. The 1836 siege there lasted thirteen days, ending when Mexican forces under General Santa Anna overwhelmed the defenders, among them Davy Crockett and James Bowie. Although the battle was a defeat for the Texian rebels, it became a rallying cry for the wider Texas Revolution.

Promethium and the art of chemical symbols

Promethium takes its symbol Pm from its name, but many elements are less predictable: lead is Pb, from the Latin plumbum, and potassium is K, from kalium. Promethium is a rare-earth metal with no stable isotopes, which is why it was only identified in the mid-20th century. Today it has niche uses, including in some luminous paints and nuclear batteries.

Darwin, Wallace and a shared discovery

Charles Darwin is the name most associated with the theory of evolution by natural selection, but he was not working in isolation. Alfred Russel Wallace arrived at strikingly similar ideas while collecting specimens in the Malay Archipelago, prompting the two men to present their findings together in 1858. Darwin's On the Origin of Species followed in 1859 and gave the theory its enduring public voice.