Beyond the answers - interesting background to this quiz

Two rivers that shaped a continent

The Nile and the Congo are among Africa's most important waterways, and they could hardly be more different. The Nile flows north for thousands of kilometres through deserts and dense cities before reaching the Mediterranean, and its annual floods supported one of the world's earliest civilisations. The Congo, by contrast, drains a vast rainforest basin in central Africa. It is the deepest river in the world, and its enormous volume makes it a lifeline for both wildlife and millions of people.

Mark Twain's most famous boy

Tom Sawyer first appeared in Mark Twain's 1876 novel, a nostalgic portrait of boyhood in a small town on the Mississippi River. Twain later gave Tom's friend Huckleberry Finn his own book, often considered one of the great American novels. Tom is mischievous, charming and forever scheming, whether whitewashing a fence or hunting for buried treasure. His adventures have never gone out of print and have been adapted for film, television and stage many times.

Vietnam's capital question

Many visitors assume Ho Chi Minh City, the country's largest metropolis, is the capital of Vietnam. In fact, Hanoi holds that role, and the distinction is a useful piece of modern history. After the country was divided in the mid-twentieth century, Hanoi served as the capital of North Vietnam, while Saigon, later renamed Ho Chi Minh City, was the capital of the South. When Vietnam reunified in 1976, Hanoi became the capital of the whole country.

Why eggs skip vitamin C

Eggs are a remarkably complete food, containing protein, fat and a wide range of vitamins and minerals. Vitamin C is the notable exception: it simply is not present in any meaningful amount. Humans cannot make vitamin C themselves, so we depend on fruits, vegetables and other plant foods to get it. That is why a diet built entirely around eggs, however nutritious, would still leave a crucial gap.