Beyond the answers - interesting background to this quiz

A wall that is really many walls

The Great Wall of China is not a single structure but a series of walls, trenches and natural barriers built and rebuilt over many centuries by different dynasties. Its most famous surviving sections date largely from the Ming dynasty. The wall served as a defence against raids from the north, and watchtowers along it allowed soldiers to send smoke or fire signals across long distances.

Deserts are not always hot

The Sahara is the largest hot desert on Earth, but deserts are defined by dryness, not temperature. Antarctica and the Arctic are polar deserts because they receive very little precipitation. The Himalayas, by contrast, form a mountain barrier across several countries, including Pakistan, India, Nepal, Bhutan and China, and they influence the climate of much of South Asia.

A calendar that keeps the seasons in step

The Gregorian calendar, introduced by Pope Gregory XIII in the 16th century, refined the earlier Julian calendar so that Easter and the seasons stayed aligned. Its leap-year rule is slightly more accurate than the older system. Today it is the most widely used civil calendar in the world, though many countries also use religious or traditional calendars alongside it.

Two sets of teeth, one lifetime

Humans typically develop two sets of teeth. The first, often called milk teeth or baby teeth, number 20 and usually appear in early childhood. They are gradually replaced by up to 32 permanent teeth, which include wisdom teeth. Milk teeth matter more than they seem to: they help children chew, speak clearly and hold space for the adult teeth growing beneath them.

Pasta with something hidden inside

Ravioli is a stuffed pasta, usually made by enclosing a filling of cheese, vegetables or meat between two thin sheets of dough. Its name comes from the Italian verb meaning "to wrap" or "to enclose". Other shapes play different roles: macaroni is tubular and often baked or boiled, while farfalle, meaning "butterflies", is pinched in the middle to look like a bow tie.