Beyond the answers - interesting background to this quiz

The creature that refuses to be found

The Yeti, often called the "abominable snowman," belongs to a long tradition of Himalayan folklore, where stories describe a large, ape-like being living in the high mountains. Expeditions have searched for physical evidence for decades, and "Yeti" footprints and scalps have turned up in monasteries and collections, though scientific testing of such remains has generally pointed to familiar animals such as bears. The legend endures partly because the Himalayas remain so vast and poorly mapped in places that the idea of a hidden species never quite dies.

Why Venus outranks Mercury

It seems counterintuitive: Mercury is closer to the Sun, yet Venus is the hottest planet in the solar system. The reason lies in Venus's thick atmosphere, which is dominated by carbon dioxide and traps heat through a runaway greenhouse effect. Surface temperatures there hover around 465 degrees Celsius, hot enough to melt lead, while Mercury swings between extremes depending on whether its surface faces the Sun. Venus is also roughly Earth's size, which is why it is sometimes called our "sister planet," despite being utterly hostile.

Salt, symbols and the logic of chemistry

Table salt's formula, NaCl, reflects a simple pairing of sodium and chlorine, but the wider system of chemical symbols follows rules that are not always obvious. Iron's symbol is Fe, from the Latin ferrum, which is why it looks nothing like the English word. Many elements carry these Latin roots: gold is Au from aurum, and lead is Pb from plumbum. The symbols were standardised over the nineteenth century so that chemists everywhere could read a formula the same way, regardless of their native language.

The Mekong, a river that crosses borders

The Mekong begins on the Tibetan Plateau and winds through China, Myanmar, Laos, Thailand, Cambodia and Vietnam before emptying into the South China Sea. It supports one of the world's largest inland fisheries and provides water and transport for tens of millions of people. Because so many countries depend on it, the river is also a source of diplomatic tension, with upstream dams affecting water flow and sediment downstream. Few rivers illustrate how geography and politics intertwine so clearly.