Given the task definition, example input & output, solve the new input case.
This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.
Example: Passage: The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. The war was fought between the colonies of British America and New France, with both sides supported by military units from their parent countries of Great Britain and France, as well as Native American allies. At the start of the war, the French North American colonies had a population of roughly 60,000 European settlers, compared with 2 million in the British North American colonies. The outnumbered French particularly depended on the Indians. Long in conflict, the metropole nations declared war on each other in 1756, escalating the war from a regional affair into an intercontinental conflict.
Output: When was the French and Indian War?
This question is based on the following sentence in the passage- The French and Indian War (1754–1763) was the North American theater of the worldwide Seven Years' War. It is a common convention to write (start year-end year) beside a historical event to understand when the event happened. You can ask questions like this one about dates, years, other numerals, persons, locations, noun phrases, verb phrases, adjectives, clauses etc. which exist in the paragraph.

New input case for you: This situation prevailed until 1639, when most of Alsace was conquered by France so as to keep it out of the hands of the Spanish Habsburgs, who wanted a clear road to their valuable and rebellious possessions in the Spanish Netherlands. Beset by enemies and seeking to gain a free hand in Hungary, the Habsburgs sold their Sundgau territory (mostly in Upper Alsace) to France in 1646, which had occupied it, for the sum of 1.2 million Thalers. When hostilities were concluded in 1648 with the Treaty of Westphalia, most of Alsace was recognized as part of France, although some towns remained independent. The treaty stipulations regarding Alsace were complex; although the French king gained sovereignty, existing rights and customs of the inhabitants were largely preserved. France continued to maintain its customs border along the Vosges mountains where it had been, leaving Alsace more economically oriented to neighbouring German-speaking lands. The German language remained in use in local administration, in schools, and at the (Lutheran) University of Strasbourg, which continued to draw students from other German-speaking lands. The 1685 Edict of Fontainebleau, by which the French king ordered the suppression of French Protestantism, was not applied in Alsace. France did endeavour to promote Catholicism; Strasbourg Cathedral, for example, which had been Lutheran from 1524 to 1681, was returned to the Catholic Church. However, compared to the rest of France, Alsace enjoyed a climate of religious tolerance.
Output:
When did the Habsburgs  sell the Sundgau territory to France?