Beyond the answers - interesting background to this quiz

Why orchestras need four very different families

The flute that sneaks into question one belongs to the woodwind family, not the strings. Western orchestras are usually divided into four sections: strings, woodwinds, brass and percussion. The string family is the largest, and its instruments produce sound when their strings vibrate - either with a bow, as with the violin and cello, or by plucking, as with a harp. The flute, by contrast, makes sound when a stream of air splits across an opening, which is why it sits firmly among the woodwinds even though it is often made of metal today.

The quiet arithmetic of blood donation

Blood type O is often called the universal donor type, but that generosity does not work in reverse. A person with type O blood can only receive type O blood, because their immune system treats A and B markers as intruders. This is why O negative blood is so prized in emergencies: it can be given to almost anyone, yet its own donors have the narrowest options. Blood banks constantly appeal for O donors precisely because their blood is so widely usable.

A river that crosses borders

The Zambezi is the fourth-longest river in Africa and flows through several countries, including Zambia, Angola, Namibia, Botswana, Zimbabwe and Mozambique, before emptying into the Indian Ocean. Along the way it plunges over Victoria Falls, one of the most spectacular waterfalls on the planet. For millions of people in southern Africa, the river is also a lifeline for fishing, farming and transport.

The invisible line that shapes maps and climates

The equator passes through thirteen countries, including the Democratic Republic of the Congo in central Africa. Places near it experience little seasonal temperature change, which is why tropical rainforests thrive there. It also influences rainfall patterns and, indirectly, where deserts and savannas form. Norway, by contrast, sits far to the north, well above the Arctic Circle, while Argentina lies deep in the southern hemisphere.