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.

Passage: Varmint hunting is an American phrase for the selective killing of non-game animals seen as pests. While not always an efficient form of pest control, varmint hunting achieves selective control of pests while providing recreation and is much less regulated. Varmint species are often responsible for detrimental effects on crops, livestock, landscaping, infrastructure, and pets. Some animals, such as wild rabbits or squirrels, may be utilised for fur or meat, but often no use is made of the carcass. Which species are varmints depends on the circumstance and area. Common varmints may include various rodents, coyotes, crows, foxes, feral cats, and feral hogs. Some animals once considered varmints are now protected, such as wolves. In the US state of Louisiana, a non-native rodent known as a nutria has become so destructive to the local ecosystem that the state has initiated a bounty program to help control the population. Question: What has the state of Louisiana done to combat the nutria?
initiated a bounty program

Passage: When World War II started, tonnage levels at the port decreased and shipping activities were suspended; however, the war did provide economic benefits for the city. Petrochemical refineries and manufacturing plants were constructed along the ship channel because of the demand for petroleum and synthetic rubber products by the defense industry during the war. Ellington Field, initially built during World War I, was revitalized as an advanced training center for bombardiers and navigators. The Brown Shipbuilding Company was founded in 1942 to build ships for the U.S. Navy during World War II. Due to the boom in defense jobs, thousands of new workers migrated to the city, both blacks and whites competing for the higher-paying jobs. President Roosevelt had established a policy of non-discrimination for defense contractors, and blacks gained some opportunities, especially in shipbuilding, although not without resistance from whites and increasing social tensions that erupted into occasional violence. Economic gains of blacks who entered defense industries continued in the postwar years. Question: Why did thousands of new workers flock to Houston?
defense jobs

Passage: From 1950 to 2011, world population increased from 2.5 billion to 7 billion and is forecast to reach a plateau of more than 9 billion during the 21st century. Sir David King, former chief scientific adviser to the UK government, told a parliamentary inquiry: "It is self-evident that the massive growth in the human population through the 20th century has had more impact on biodiversity than any other single factor." At least until the middle of the 21st century, worldwide losses of pristine biodiverse land will probably depend much on the worldwide human birth rate. Question: What is the forecast plateau that the population will reach during the 21st century?
more than 9 billion