Beyond the answers - interesting background to this quiz

The element that hides in plain sight

Krypton takes its name from the Greek word for "hidden", and it lives up to it: it is a colourless, odourless noble gas that makes up only a tiny trace of the air around us. It was discovered in 1898 by the British chemists William Ramsay and Morris Travers, who were hunting for the missing members of the noble gas family. Today it turns up in high-performance lighting and photographic flash lamps.

A medical discovery that took centuries to be believed

William Harvey's 1628 work on the circulation of blood overturned more than a thousand years of medical teaching. The ancient physician Galen had held that blood was continually produced in the liver and consumed by the body, but Harvey showed through dissection and experiment that the heart pumps blood in a closed loop around the body. His ideas were initially met with scepticism, yet they became the foundation of modern physiology.

The ocean's top predator

The sperm whale is the largest predator on Earth, and its size is matched by its hunting habits. It dives to great depths to feed on squid, including the giant squid, and its enormous head houses the largest brain of any animal. Its name comes from spermaceti, the waxy substance found in that head, which was once highly prized by whalers.

Dickens and the making of a Christmas icon

Ebenezer Scrooge first appeared in Charles Dickens's A Christmas Carol, published in December 1843. The story of the miser who is visited by three spirits and learns to change his ways struck a chord in Victorian Britain, where poverty and harsh working conditions were pressing social issues. It has never been out of print since and has been adapted countless times for stage and screen.