Beyond the answers - interesting background to this quiz

The gas that shaped life on Earth

Oxygen makes up roughly a fifth of the air around us, yet it was almost absent from Earth's early atmosphere. It accumulated largely through photosynthesis, first in simple organisms and later in plants, and complex animal life depends on it for respiration. That slow transformation of the atmosphere is one reason breathable air is treated as a defining feature of our planet.

Rivers that cross borders

The Mekong begins on the Tibetan Plateau and runs through China before continuing into Southeast Asia, where it supports some of the world's most productive fisheries. The Volga takes a very different route, winding through Russia before emptying into the Caspian Sea, and it is widely regarded as the longest river in Europe. Both waterways have shaped trade, farming and settlement along their banks for centuries.

The Bahamas and its capital

The Bahamas is an archipelago of hundreds of islands and cays in the Atlantic, southeast of Florida. Its capital, Nassau, sits on New Providence Island and has long served as the country's political and commercial centre. The name Nassau honours a historic European royal house, a reminder of the colonial era that left its mark on much of the Caribbean.

The whale that breaks records

The blue whale is not just the largest whale but the largest animal known to have lived, surpassing even the biggest dinosaurs by mass. It feeds mainly on tiny krill, which it filters from seawater through baleen plates. Despite its enormous size, it is a graceful swimmer, and its low-frequency calls can travel great distances underwater.

Patterns hidden in plain sight

Sequences like 1, 2, 4, 7, 11 reward patience more than mathematical talent. The gaps between the numbers grow steadily, and spotting that rhythm is often enough to predict what comes next. Such puzzles appear in aptitude tests and classic recreational maths, where the trick is usually simpler than it first looks.