Question: It has been proved that each class is strictly included into the next. For instance, testing when we assume that the behavior of the implementation under test can be denoted by a deterministic finite-state machine for some known finite sets of inputs and outputs and with some known number of states belongs to Class I (and all subsequent classes). However, if the number of states is not known, then it only belongs to all classes from Class II on. If the implementation under test must be a deterministic finite-state machine failing the specification for a single trace (and its continuations), and its number of states is unknown, then it only belongs to classes from Class III on. Testing temporal machines where transitions are triggered if inputs are produced within some real-bounded interval only belongs to classes from Class IV on, whereas testing many non-deterministic systems only belongs to Class V (but not all, and some even belong to Class I). The inclusion into Class I does not require the simplicity of the assumed computation model, as some testing cases involving implementations written in any programming language, and testing implementations defined as machines depending on continuous magnitudes, have been proved to be in Class I. Other elaborated cases, such as the testing framework by Matthew Hennessy under must semantics, and temporal machines with rational timeouts, belong to Class II.
Is there an answer to this question: The inclusion into Class I requires what?

Answer: unanswerable


Question: Ethnic Russians constitute 25.5% of the country's current population and 58.6% of the native Estonian population is also able to speak Russian. In all, 67.8% of Estonia's population can speak Russian. Command of Russian language, however, is rapidly decreasing among younger Estonians (primarily being replaced by the command of English). For example, if 53% of ethnic Estonians between 15 and 19 claim to speak some Russian, then among the 10- to 14-year-old group, command of Russian has fallen to 19% (which is about one-third the percentage of those who claim to have command of English in the same age group).
Is there an answer to this question: What has the percentage of 10-14 year olds in Russia fallen to?

Answer: unanswerable


Question: Antarctica has no indigenous population and there is no evidence that it was seen by humans until the 19th century. However, belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe, Asia and North Africa—had existed since the times of Ptolemy (1st century AD), who suggested the idea to preserve the symmetry of all known landmasses in the world. Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size.
Is there an answer to this question: Who suggested Australis Terra?

Answer: unanswerable


Question: From 1904 to 1907, the Herero and the Namaqua took up arms against the Germans and in calculated punitive action by the German occupiers, the 'first genocide of the Twentieth Century' was committed. In the Herero and Namaqua genocide, 10,000 Nama (half the population) and approximately 65,000 Hereros (about 80% of the population) were systematically murdered. The survivors, when finally released from detention, were subjected to a policy of dispossession, deportation, forced labour, racial segregation and discrimination in a system that in many ways anticipated apartheid.
Is there an answer to this question: In what year did "the first genocide of the Twentieth Century" end?

Answer:
unanswerable