Beyond the answers - interesting background to this quiz

A capital that shares its country's name

Guatemala City is one of a handful of capitals in the Americas that carry the same name as their country, alongside Mexico City and Panama City. It sits in a highland valley in the south of Guatemala and is by far the country's largest urban area. The city has been rebuilt more than once after earthquakes, which is one reason its architecture mixes colonial remains with modern construction.

Indiana Jones and the actor who made him famous

Harrison Ford has played the archaeologist-adventurer in more films than anyone else, beginning with Raiders of the Lost Ark in 1981. The character was created by George Lucas and Steven Spielberg, who wanted a hero in the spirit of the old Saturday matinee serials. Ford was not the first choice for the part, but his performance defined the role so thoroughly that later reboots and sequels still orbit around it.

The river that crosses a continent

The Amazon flows through Brazil, but it also passes through Peru and Colombia, and its vast drainage basin reaches into several more South American countries. It carries more water than any other river on Earth, and its outflow is so powerful that the sea near its mouth is noticeably fresher than the surrounding ocean. The river and its rainforest support an estimated one in ten known species on the planet.

Retinol, vitamin A and the chemistry of sight

Retinol is one form of vitamin A, a group of related compounds that the body needs for vision, skin health and immune function. The name comes from its role in the retina, where a derivative of vitamin A is essential for converting light into the signals the brain reads as images. Deficiency remains a serious public health issue in parts of the world, which is why vitamin A is often added to foods such as cooking oil and rice.

Singin' in the Rain and its unusual directing credit

The 1952 musical is credited to both Gene Kelly and Stanley Donen, which is why "both" is the correct answer here. Kelly, who also starred and choreographed, and Donen shared the directing duties during a period when the two worked closely together at MGM. The film's famous title number, performed by Kelly with an umbrella in the rain, is often cited as one of the great sequences in cinema history.