Question: Extract the answer to the question from the following context. Question: Because of the necessary boost it needs, what is the most basic thing that is needed to produce that boost? Context: A climbing elevator is a self-ascending elevator with its own propulsion. The propulsion can be done by an electric or a combustion engine. Climbing elevators are used in guyed masts or towers, in order to make easy access to parts of these constructions, such as flight safety lamps for maintenance. An example would be the Moonlight towers in Austin, Texas, where the elevator holds only one person and equipment for maintenance. The Glasgow Tower an observation tower in Glasgow, Scotland also makes use of two climbing elevators.
Answer: electric or a combustion engine

Question: Extract the answer to the question from the following context. Question: Which happened later, the single-grain experiment or the discovery that the amino acid tryptophan aids the well-being of mice? Context: In the early 20th century, Carl von Voit and Max Rubner independently measured caloric energy expenditure in different species of animals, applying principles of physics in nutrition. In 1906, Edith G. Willcock and Frederick Hopkins showed that the amino acid tryptophan aids the well-being of mice but it did not assure their growth. In the middle of twelve years of attempts to isolate them, Hopkins said in a 1906 lecture that "unsuspected dietetic factors," other than calories, protein, and minerals, are needed to prevent deficiency diseases. In 1907, Stephen M. Babcock and Edwin B. Hart conducted the single-grain experiment, which took nearly four years to complete.
Answer: single-grain experiment

Question: Extract the answer to the question from the following context. Question: what is the first time period mentioned? Context: Ultimately, World War I created a decisive break with the old world order that had emerged after the Napoleonic Wars, which was modified by the mid-19th century's nationalistic revolutions. The results of World War I would be important factors in the development of World War II approximately 20 years later. More immediate to the time, the partitioning of the Ottoman Empire was a political event that redrew the political boundaries of West Asia. The huge conglomeration of territories and peoples formerly ruled by the Sultan of the Ottoman Empire was divided into several new nations. The partitioning brought the creation of the modern Arab world and the Republic of Turkey. The League of Nations granted France mandates over Syria and Lebanon and granted the United Kingdom mandates over Mesopotamia and Palestine (which was later divided into two regions: Palestine and Transjordan). Parts of the Ottoman Empire on the Arabian Peninsula became parts of what are today Saudi Arabia and Yemen.
Answer:
mid-19th century's