Problem: Small-scale artisanal mining of gold is another source of dangerous child labour in poor rural areas in certain parts of the world. This form of mining uses labour-intensive and low-tech methods. It is informal sector of the economy. Human Rights Watch group estimates that about 12 percent of global gold production comes from artisanal mines. In west Africa, in countries such as Mali - the third largest exporter of gold in Africa - between 20,000 and 40,000 children work in artisanal mining. Locally known as orpaillage, children as young as 6 years old work with their families. These children and families suffer chronic exposure to toxic chemicals including mercury, and do hazardous work such as digging shafts and working underground, pulling up, carrying and crushing the ore. The poor work practices harm the long term health of children, as well as release hundreds of tons of mercury every year into local rivers, ground water and lakes. Gold is important to the economy of Mali and Ghana. For Mali, it is the second largest earner of its export revenue. For many poor families with children, it is the primary and sometimes the only source of income.
What is the third largest exporter of gold in Africa?
The answer is the following: Mali

Problem: The evolutionary relationships and heredity of a group of organisms is called its phylogeny. Phylogenetic studies attempt to discover phylogenies. The basic approach is to use similarities based on shared inheritance to determine relationships. As an example, species of Pereskia are trees or bushes with prominent leaves. They do not obviously resemble a typical leafless cactus such as an Echinocactus. However, both Pereskia and Echinocactus have spines produced from areoles (highly specialised pad-like structures) suggesting that the two genera are indeed related.
What are areoles?
The answer is the following: pad-like structures

Problem: By 500 BC, the Persian Empire controlled the Greek city states in Asia Minor and had made territorial gains in the Balkans and Eastern Europe proper as well. Attempts by some of the Greek city-states of Asia Minor to overthrow Persian rule failed, and Persia invaded the states of mainland Greece in 492 BC, but was forced to withdraw after a defeat at the Battle of Marathon in 490 BC. A second invasion by the Persians followed in 480 BC. Despite a heroic resistance at Thermopylae by Spartans and other Greeks led by King Leonidas, and a simultaneous naval engagement at Artemisium,[page needed] Persian forces occupied Athens, which had been evacuated in time, as well as briefly overrunning half of Greece. Following decisive Greek victories in 480 and 479 BC at Salamis, Plataea, and Mycale, the Persians were forced to withdraw for a second time, marking their eventual withdrawal from all of their European territories. Led by Athens and Sparta, the Greek victories in the Greco-Persian Wars are considered a pivotal moment in world history, as the 50 years of peace that followed are known as Golden Age of Athens, the seminal period of ancient Greece that laid many of the foundations of Western civilization.
After the Persians left Europe, the time period that followed was called what?
The answer is the following: Golden Age of Athens

Problem: Imperial College Union, the students' union at Imperial College, is run by five full-time sabbatical officers elected from the student body for a tenure of one year, and a number of permanent members of staff. The Union is given a large subvention by the university, much of which is spent on maintaining around 300 clubs, projects and societies. Examples of notable student groups and projects are Project Nepal which sends Imperial College students to work on educational development programmes in rural Nepal and the El Salvador Project, a construction based project in Central America. The Union also hosts sports-related clubs such as Imperial College Boat Club and Imperial College Gliding Club.
What is the official name of the student's union?
The answer is the following:
Imperial College Union