Beyond the answers - interesting background to this quiz

Where the line cuts through

The equator crosses the territory of a number of countries, and São Tomé and Príncipe is one of them. This small island nation lies in the Gulf of Guinea off the west coast of Africa, and the equator passes through the waters of its exclusive economic zone near the island of Príncipe. That location gives it a hot, humid tropical climate with little seasonal temperature variation.

A river that crosses borders

The Mekong begins on the Tibetan Plateau and runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before emptying into the South China Sea. It ranks among the longest rivers in Asia and supports one of the world's largest inland fisheries. In Vietnam it fans out into the Mekong Delta, a fertile region sometimes called the country's rice bowl.

Copper and its chemical shorthand

The symbol Cu for copper comes from the Latin word cuprum, which itself traces back to the island of Cyprus, a place famous in antiquity for its copper mines. Copper was one of the first metals humans worked, and it remains essential today in electrical wiring, plumbing and coinage. Its distinct reddish colour and high conductivity make it easy to identify.

Niacin and the B vitamins

Niacin, also called vitamin B3, is a water-soluble vitamin that the body needs for converting food into energy and for keeping skin and nerves healthy. It occurs naturally in meat, fish, eggs, whole grains and nuts. A severe deficiency of niacin causes pellagra, a disease historically associated with diets based heavily on untreated maize.

From Rome to Russia

Ovid, or Ovidius in Latin, was a Roman poet best known for the Metamorphoses, a long narrative poem drawing on Greek and Roman myths. He was exiled by the emperor Augustus to Tomis on the Black Sea, where he spent his final years. Centuries later, Tolstoy's War and Peace wove together fictional families and real historical events during Napoleon's invasion of Russia.