Beyond the answers - interesting background to this quiz

The river that bends like a bow

The Niger is West Africa's principal river, rising in the highlands of Guinea and flowing in a great curve through Mali, Niger and Nigeria before emptying into the Gulf of Guinea. Its unusual shape puzzled European geographers for centuries, since it runs surprisingly close to the sea before turning inland. For traders and empires along its banks, from Timbuktu to the delta ports, it was less a puzzle than a highway.

Heat you can measure

The Scoville scale, devised by the American pharmacist Wilbur Scoville in 1912, rates pungency by how much a chilli extract must be diluted before the heat is no longer detectable. Bell peppers sit at the very bottom, effectively zero. The ghost pepper, a hybrid first cultivated in northeast India, once held the record for the world's hottest chilli before several hotter varieties displaced it.

Why gold is Au

Gold's chemical symbol, Au, comes from the Latin aurum, meaning gold, and it sits alongside other elements whose symbols betray their Latin roots, such as iron (Fe, ferrum) and lead (Pb, plumbum). Mercury, meanwhile, is the only metal that is liquid at ordinary room temperature, which is why it was long used in thermometers and barometers before health concerns curbed its use.

Tempo with a built-in brake

Italian has supplied most of music's tempo vocabulary. Allegro means fast and lively, andante means a walking pace, while accelerando instructs the performer to gradually speed up. The endings matter: an -ando marking describes a process rather than a fixed speed, so accelerando is a direction to change, not a setting to hold.

A currency that left its mark

The Deutsche Mark was introduced in West Germany in 1948 and became a symbol of the postwar economic recovery known as the Wirtschaftswunder. It remained the currency of a reunified Germany until the euro replaced it in physical form in 2002. Even today, Germans still occasionally speak of "Mark" prices when converting in their heads.