Thomas Malthus was a writer and philosopher who lived in England during the late eighteenth and early nineteenth centuries. He is most widely remembered for his essay titled An Essay on the Principle of Population. In this essay, he states that sooner or later the population of the earth would exceed the supply of resources needed to keep the population alive. In what is known as a "Malthusian catastrophe," he predicted that the continuing rise in population would precede a period of intense warfare and famine, which would then bring the population back to more manageable levels. His views were influential and affected the economic and sociopolitical thinking of his time.

Following his return to Russia from exile in the spring of 1917, Lenin published his famous April Theses, in which he promised the Russian people “Peace! Land! Bread!” During World War One, the Russian people suffered horribly in unprecedented numbers; when Lenin returned to Russia, a large portion of the Russian population was ready for an end to the war with the Central Powers ("Peace!"); an end to the abhorrent policies of land distribution that saw the majority of the population unable to own property ("Land!"); and an end to the widespread famine that had gripped Russia in the previous two years ("Bread!").

Toussaint Louverture was the leader of the Haitian Revolution. He was a freed former slave who incited the Haitian slave community to rebellion against the French authorities. He was eventually captured and taken to France, where he died shortly after, but his legacy lived on and France was unable to suppress the rebellion, primarily due to massive losses sustained from Yellow Fever. Haiti has been an independent nation ever since.

David Livingstone and Henry Morton Stanley were two British explorers and missionaries who explored vast swathes of Central Africa and, amongst other things, established that Lake Tanganyika was not the source of the Nile River. (The source of the Nile River was a topic of much interest in the late-nineteenth century Europe.)

The Medici family was an aristocratic family and banking dynasty that rose to prominence in fourteenth-century Florence under the leadership of Cosimo de Medici. The Medici family would go on to produce several popes, two queens of France, and the dynasty that ruled over Grand Duchy of Tuscany for two hundred years.

Frederick the Great reigned over the Kingdom of Prussia from 1740 to 1786 and, along with Catherine the Great, is most commonly remembered as an “enlightened despot”; Catherine, for her own part, reigned as Tsarina of Russia from 1762 to 1796; William Pitt the Younger served as British Prime Minister at various times throughout the late eighteenth and early nineteenth centuries; and Louis XIV reigned over France for an astonishing seventy-two years from 1643 until his death in 1715. Of the presented answer choices, only King Charles II of England did not rule in the eighteenth century. Charles II reigned over England, Ireland, and Scotland at a time of great upheaval in British history. Depending on who you ask, his reign even began in 1649, following the execution of his father at the climax of the English Civil War, or, more practically, in 1660, following the death of Oliver Cromwell.

German unification was achieved largely as a result of the territorial and political ambitions of its “iron chancellor,” Otto von Bismarck. German nationalism had long existed as a tenuous and optimistic ideal, but the fragmented nature of the Holy Roman Empire and the German principalities made such a unification very difficult. It was not until the ascension of Prussia as one of the preeminent powers in Europe that German national unification was anything more than a pipe dream. Bismarck governed Prussia effectively and realized the way to engender German nationalism was to create a common enemy—France and Austria. A series of wars with both these countries created support for a unified Germany.

Hammurabi is the most famous of the Babylonian Kings who ruled vast areas of Ancient Mesopotamia from about 1850 B.C.E. until the Sack of Babylon in 1531 B.C.E. He is mostly remembered for the introduction of Hammurabi’s Code of Laws - one of the earliest known established legal codes in world history. 

Queen Victoria reigned over Britain from 1837-1901; Andrew Jackson was President of the United States from 1829-1837; Pedro II reigned over the nation of Brazil for the majority of the Nineteenth Century; Napoleon Bonaparte was Emperor of France from 1804-1814. Of these options only Frederick the Great, King of Prussia, was not in power in the Nineteenth Century. Frederick reigned over Prussia from 1740-1786. 

Pedro II was the most famous King of the Brazilian monarchy and his reign lasted for much of the Nineteenth Century. However, he was not king at the turn of the century. Roosevelt was an American President during the Great Depression and World War Two; Pol Pot was a Cambodian ruler in the mid-twentieth century who is most often remembered for the terrible atrocities and genocide committed under his direction; Josef Stalin was the leader of the Socialist Party of the Soviet Union in the decades immediately before, during, and after World War Two; Nikita Khrushchev succeeded Josef Stalin in the 1950s.