This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Example Input: Passage: Due to the expansion of trade and its geographical proximity, Kiev became the most important trade centre and chief among the communes; therefore the leader of Kiev gained political "control" over the surrounding areas. This princedom emerged from a coalition of traditional patriarchic family communes banded together in an effort to increase the applicable workforce and expand the productivity of the land. This union developed the first major cities in the Rus' and was the first notable form of self-government. As these communes became larger, the emphasis was taken off the family holdings and placed on the territory that surrounded. This shift in ideology became known as the verv'. Question: How did the leader of Kiev gain political control?
Example Output: Due to the expansion of trade

Example Input: Passage: The Wagner tuba, a modified member of the horn family, appears in Richard Wagner's cycle Der Ring des Nibelungen and several other works by Strauss, Bela Bartok, and others; it has a prominent role in Anton Bruckner's Symphony No. 7 in E Major. Cornets appear in Pyotr Ilyich Tchaikovsky's ballet Swan Lake, Claude Debussy's La Mer, and several orchestral works by Hector Berlioz. Unless these instruments are played by members doubling on another instrument (for example, a trombone player changing to euphonium for a certain passage), orchestras will use freelance musicians to augment their regular rosters. Question: What is the name of the modified member of the horn family appearing in several works by Strauss?
Example Output: The Wagner tuba

Example Input: Passage: Deforestation and forest fires are a problem in many areas, as is the continual spread of the eucalyptus tree, a species imported from Australia, actively promoted by the paper industry since the mid-20th century. Galicia is one of the more forested areas of Spain, but the majority of Galicia's plantations, usually growing eucalyptus or pine, lack any formal management. Massive eucalyptus, especially Eucalyptus globulus plantation, began in the Francisco Franco era, largely on behalf of the paper company Empresa Nacional de Celulosas de Espana (ENCE) in Pontevedra, which wanted it for its pulp. Wood products figure significantly in Galicia's economy. Apart from tree plantations Galicia is also notable for the extensive surface occupied by meadows used for animal husbandry, especially cattle , an important activity. Hydroelectric development in most rivers has been a serious concern for local conservationists during the last decades. Question: What kind of development on rivers are conservationists concerned about?
Example Output:
Hydroelectric