The lower (Triassic) boundary is set by the Permian–Triassic extinction event, during which approximately 90% to 96% of marine species and 70% of terrestrial vertebrates became extinct. It is also known as the "Great Dying" because it is considered the largest mass extinction in the Earth's history. The upper (Cretaceous) boundary is set at the Cretaceous–Tertiary (KT) extinction event (now more accurately called the Cretaceous–Paleogene (or K–Pg) extinction event), which may have been caused by the impactor that created Chicxulub Crater on the Yucatán Peninsula. Towards the Late Cretaceous large volcanic eruptions are also believed to have contributed to the Cretaceous–Paleogene extinction event. Approximately 50% of all genera became extinct, including all of the non-avian dinosaurs.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is the possible cause of the upper Cretaceous extinction event ?
Ah, so.. K–Pg) extinction

With French, Belgian and Portuguese activity in the lower Congo River region undermining orderly incursion of tropical Africa, the Berlin Conference of 1884–85 was held to regulate the competition between the European powers in what was called the "Scramble for Africa" by defining "effective occupation" as the criterion for international recognition of territorial claims. The scramble continued into the 1890s, and caused Britain to reconsider its decision in 1885 to withdraw from Sudan. A joint force of British and Egyptian troops defeated the Mahdist Army in 1896, and rebuffed a French attempted invasion at Fashoda in 1898. Sudan was nominally made an Anglo-Egyptian Condominium, but a British colony in reality.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What was the period of European empires competing to control Africa called?
Ah, so.. the "Scramble for Africa"

According to Paul Martin, Sr., by the end of the 1970s the Queen was worried that the Crown "had little meaning for" Pierre Trudeau, the Canadian Prime Minister. Tony Benn said that the Queen found Trudeau "rather disappointing". Trudeau's supposed republicanism seemed to be confirmed by his antics, such as sliding down banisters at Buckingham Palace and pirouetting behind the Queen's back in 1977, and the removal of various Canadian royal symbols during his term of office. In 1980, Canadian politicians sent to London to discuss the patriation of the Canadian constitution found the Queen "better informed ... than any of the British politicians or bureaucrats". She was particularly interested after the failure of Bill C-60, which would have affected her role as head of state. Patriation removed the role of the British parliament from the Canadian constitution, but the monarchy was retained. Trudeau said in his memoirs that the Queen favoured his attempt to reform the constitution and that he was impressed by "the grace she displayed in public" and "the wisdom she showed in private".
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): In what year did Pierre Trudeau cease to be Canada's prime minister?
Ah, so..
unanswerable