In this task, you're given a context, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both context and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the context or linked information.

Context: Warrington spent most of his career on the Texas frontier and served under Colonel Ranald S. Mackenzie during the Texas-Indian Wars of the 1870s. Link Information: On February 25, 1871, he assumed command of the 4th U.S. Cavalry at Fort Richardson in Jacksboro, Texas. Answer: the 4th U.S. Cavalry
What units did the Colonel Warrington served under inn the Texas-Indian Wars command?

Context: Massey joined the Canadian Army at the outbreak of World War I, Link Information: First World War, the Great War, the Seminal Catastrophe, and initially in North America as the European War, was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918. Answer: 4
How long did the war in which Massey joined the Canadian Army last?

Context: Clayoquot Sound was listed as a Biosphere Reserve in 2000 Link Information: none Answer: none

How many students were enrolled in Carleton University the year Clayoquot Sound was listed as a Biosphere Reserve?