Beyond the answers - interesting background to this quiz

The many everyday uses of a familiar white powder

Sodium bicarbonate, better known as baking soda, is a remarkably versatile compound. In the kitchen it reacts with acids to release carbon dioxide, which is what makes cakes and breads rise. It also works as a mild abrasive, a deodoriser and an antacid, which is why a box of it tends to live in more than one room of the house.

A Roman general who refused to stay down

Russell Crowe won the Academy Award for Best Actor for his role in Gladiator, playing the fictional general Maximus. The film, directed by Ridley Scott, imagines a former commander of the Roman army who is betrayed and sold into slavery, then fights his way up through the arena. Its blend of revenge drama and historical spectacle revived Hollywood's appetite for sword-and-sandal epics.

The tallest waterfall on the continent

Yosemite Falls in California drops in three tiers, and its total height makes it the highest waterfall in North America. It is fed largely by snowmelt, so its flow changes dramatically through the year, peaking in late spring and sometimes thinning to a trickle by late summer. The surrounding national park was shaped by glaciers, which carved the granite valley the falls pour into.

Where Europe ends and Asia begins

The boundary between Europe and Asia is a matter of convention rather than a single obvious line. The Ural Mountains are often treated as the northern part of that divide, while the Caucasus Mountains mark part of the southern stretch between the Black Sea and the Caspian Sea. Because it is a definition rather than a physical fact, different sources draw the line in slightly different places.

A river that crosses more than one border

The Congo River is the second-longest river in Africa and drains a vast basin covering several countries. It flows through the Republic of the Congo and the Democratic Republic of the Congo, and it has long served as a major transport route through dense rainforest. Its depth and volume make it one of the most powerful rivers in the world.