Beyond the answers - interesting background to this quiz

A capital built from scratch

Brasília is the answer to the Brazil question, and it is one of the few capital cities in the world designed and built specifically for that purpose in the twentieth century. Before it opened in 1960, Brazil's capital was Rio de Janeiro. The new city, laid out in a deliberate airplane-like plan by urban planner Lúcio Costa with landmark buildings by Oscar Niemeyer, was meant to pull development inland and give the country a modern, forward-looking symbol.

The river that crosses borders

The Mekong flows through six countries: China, Myanmar, Laos, Thailand, Cambodia and Vietnam. That makes it one of Asia's great international waterways, and it supports fishing and farming for tens of millions of people. The river's lower basin is also home to the world's largest inland fishery, which is one reason debates about dams and water management along its course attract so much attention.

A milestone in medicine

The first human heart transplant was performed in 1967 by South African surgeon Christiaan Barnard at Groote Schuur Hospital in Cape Town. The patient, Louis Washkansky, survived for 18 days before dying of pneumonia. The operation made headlines worldwide and opened a new era in transplant surgery, though early survival rates were low until better drugs for suppressing the immune system were developed.

Robots with rules

Isaac Asimov, the science fiction writer behind the Three Laws of Robotics, introduced them in a 1942 short story called "Runaround." The laws state that a robot may not injure a human, must obey human orders unless they conflict with the first law, and must protect its own existence unless that conflicts with the first two. What made the idea so influential was not the rules themselves but the stories Asimov built around robots finding clever ways to bend or break them.

Rivers, currencies and coastlines

The Amazon, the Yen and Finland's Baltic coastline each point to how geography and economics overlap. The Amazon drains parts of several South American countries, with the largest share in Brazil, though it also runs through Peru and Colombia. Japan's currency, the yen, has been a major reserve currency for decades. Finland's Baltic coast, meanwhile, includes the Gulf of Bothnia and the Gulf of Finland, giving the country a long maritime border with Sweden and Russia.