Beyond the answers - interesting background to this quiz

The gold that never fades

Gustav Klimt painted "The Kiss" around 1907-1908, during the height of his so-called Golden Phase. The shimmering surface comes partly from real gold leaf applied to the canvas, a technique influenced by Byzantine mosaics Klimt had seen in Ravenna. The painting now hangs in the Belvedere in Vienna and is one of the most reproduced artworks in the world.

An element with a misleading name

Bismuth carries the chemical symbol Bi and sits in group 15 of the periodic table, alongside nitrogen and phosphorus. Its name likely derives from the old German "wismut," though the exact origin is debated. Bismuth is unusual among heavy metals for being relatively non-toxic, which is why it appears in some medicines and in the pearlescent pigments of cosmetics.

The organ you live in

Skin is the body's largest organ, covering roughly two square metres in an average adult and accounting for about 15 percent of body weight. It works as a barrier, a temperature regulator and a sensory network all at once. The liver, often mistaken for the largest organ, is actually the largest internal organ.

Why Neptune takes its time

A year on Neptune lasts about 165 Earth years, since the planet orbits the Sun at an average distance of roughly 4.5 billion kilometres. Mercury, by contrast, completes a lap in just 88 Earth days. This vast difference in orbital period is why the outer planets are sometimes called the "slow" worlds of the solar system.

Franklin and the lending library

Benjamin Franklin and a group of friends founded the Library Company of Philadelphia in 1731, a subscription library that let members pool their books and share the cost. It is widely regarded as the first successful lending library of its kind in America. Franklin later described it as one of his proudest achievements.