Beyond the answers - interesting background to this quiz

A rainforest shared across borders

The Amazon is often described as if it belonged to a single country, but the quiz answer only tells part of the story. The basin spans several South American nations, with Bolivia among them - which is why it appears as the correct option here. Brazil holds the largest share of the rainforest, while Peru and Colombia also contain significant portions. The river system that drains it is the largest on Earth by volume.

The Blue Nile's highland source

Lake Tana sits in the Ethiopian highlands and is widely recognised as the source of the Blue Nile, the branch that supplies most of the Nile's water during flood season. From there the river carves its way through dramatic gorges before meeting the White Nile at Khartoum in Sudan. The White Nile, by contrast, traces back to the Lake Victoria region much further south.

Venice as Shakespeare's stage

Shakespeare set Othello partly in Venice, a choice that gave the play a cosmopolitan backdrop of trade, diplomacy and foreign military service. Venice in the late sixteenth century was a wealthy republic known for its merchants and its dealings with the Ottoman world. Othello himself is a Moorish general employed by the Venetian state - a detail that shapes much of the play's tension.

Egypt's currency and its neighbours

The Egyptian pound takes its name from the British pound, reflecting the period of British influence in Egypt. One pound divides into 100 piastres, and the currency has been issued in various forms since the nineteenth century. It is worth noting that several other countries in the region use different currencies - the dinar and the dirham appear in this quiz as decoys, and both are real monetary units used elsewhere in the Middle East and North Africa.

Radon, the invisible gas

Radon's chemical symbol is Rn, and unlike its periodic neighbours radium (Ra) and rhodium (Rh), it is a noble gas. It occurs naturally as a decay product of uranium in soil and rock, and can accumulate in buildings, particularly basements. Because it is colourless and odourless, it is usually detected through testing rather than noticed directly.