Beyond the answers - interesting background to this quiz

The flag that refuses to be a rectangle

Nepal's flag is the world's only national flag that is not a quadrilateral. It consists of two stacked triangular pennants, a design that echoes the traditional flags of the country's two major ruling dynasties. The crimson field stands for bravery and is bordered in blue, while the moon and sun symbols represent the hope that Nepal will endure as long as those celestial bodies.

A garment that marked a Roman woman's status

The stola was the long, sleeveless tunic worn by married women in ancient Rome, draped over an undergarment called the tunica. Wearing it was a sign of respectable status, and it was closely tied to the idea of the matrona, the Roman wife and mother. Women who had lost their standing, such as those convicted of adultery, could be forbidden from wearing it.

A lake that holds a fifth of the world's unfrozen fresh water

Lake Baikal, in the Russian region of Siberia, is the deepest and oldest freshwater lake on Earth, and by volume the largest. It contains roughly one fifth of the planet's unfrozen surface fresh water, more than all of North America's Great Lakes combined. Its great depth, over 1,600 metres at its deepest point, explains how a single lake can hold so much.

Chlorine and its easily confused neighbours

The symbol Cl belongs to chlorine, a greenish-yellow gas used to disinfect drinking water and swimming pools. It is often mixed up with calcium, whose symbol is Ca, and copper, Cu. All three appear on the periodic table in different groups, which is why their symbols share letters but never the exact same pairing.

A wreck that reshaped safety at sea

The Titanic struck an iceberg and sank in the North Atlantic in April 1912 during its maiden voyage from Southampton to New York. More than 1,500 people died. The disaster led to major changes in maritime safety, including the requirement that ships carry enough lifeboats for everyone on board and that radios be manned around the clock.