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: In the mid-1950s, Frank Burnet, inspired by a suggestion made by Niels Jerne, formulated the clonal selection theory (CST) of immunity. On the basis of CST, Burnet developed a theory of how an immune response is triggered according to the self/nonself distinction: "self" constituents (constituents of the body) do not trigger destructive immune responses, while "nonself" entities (e.g., pathogens, an allograft) trigger a destructive immune response. The theory was later modified to reflect new discoveries regarding histocompatibility or the complex "two-signal" activation of T cells. The self/nonself theory of immunity and the self/nonself vocabulary have been criticized, but remain very influential. Question: What property of T cells caused modification of CST?
Example Output: the complex "two-signal" activation

Example Input: Passage: Since the early 1950s on conventional carriers it has been the practice to recover aircraft at an angle to port of the axial line of the ship. The primary function of this angled deck is to allow aircraft that miss the arresting wires, referred to as a bolter, to become airborne again without the risk of hitting aircraft parked forward. The angled deck allows the installation of one or two "waist" catapults in addition to the two bow cats. An angled deck also improves launch and recovery cycle flexibility with the option of simultaneous launching and recovery of aircraft. Question: How many "waist" catapults can be installed with an angled deck?
Example Output: one or two

Example Input: Passage: During the period from 2000–2005 it is estimated that 49,722 people left the state for the United States. Some 82,000 people are thought to have immigrated to the state from 2000–2005 mainly coming from Veracruz (17.6%), United States (16.2%), Durango (13.2%), Coahuila (8.0%) and Chiapas (4.5%). It is believed that there is a large number of undocumented immigrants in that state the come from Central and South America which mainly settle in Ciudad Juárez. According to the 2005 census, the population grew 1.06% from 2000 to 2005. The state has an uneven settlement of people and the lowest population density of any Mexican state; according to the 2005 census there were 12 people per km2. Of all the 3,241,444 people in the state, two-thirds (2,072,129) live in the cities of Ciudad Juárez and Chihuahua. Only three other cities have populations over 100,000: Parral 101,147, Cuauhtémoc 105,725, and Delicias 108,187. Question: Which are the largest two cities in the state?
Example Output:
Ciudad Juárez and Chihuahua