instruction:
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.
question:
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?
answer:
the complex "two-signal" activation


question:
Passage: By August 1805, Napoleon had realized that the strategic situation had changed fundamentally. Facing a potential invasion from his continental enemies, he decided to strike first and turned his army's sights from the English Channel to the Rhine. His basic objective was to destroy the isolated Austrian armies in Southern Germany before their Russian allies could arrive. On 25 September, after great secrecy and feverish marching, 200,000 French troops began to cross the Rhine on a front of 260 km (160 mi). Austrian commander Karl Mack had gathered the greater part of the Austrian army at the fortress of Ulm in Swabia. Napoleon swung his forces to the southeast and the Grande Armée performed an elaborate wheeling movement that outflanked the Austrian positions. The Ulm Maneuver completely surprised General Mack, who belatedly understood that his army had been cut off. After some minor engagements that culminated in the Battle of Ulm, Mack finally surrendered after realizing that there was no way to break out of the French encirclement. For just 2000 French casualties, Napoleon had managed to capture a total of 60,000 Austrian soldiers through his army's rapid marching. The Ulm Campaign is generally regarded as a strategic masterpiece and was influential in the development of the Schlieffen Plan in the late 19th century. For the French, this spectacular victory on land was soured by the decisive victory that the Royal Navy attained at the Battle of Trafalgar on 21 October. After Trafalgar, Britain had total domination of the seas for the duration of the Napoleonic Wars. Question: By August 1805, Napoleon changed the primary target of his army's efforts from the English Channel to what area?
answer:
the Rhine


question:
Passage: An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a naval force to project air power worldwide without depending on local bases for staging aircraft operations. Aircraft carriers are expensive to build and are critical assets. Aircraft carriers have evolved from converted cruisers to nuclear-powered warships that carry numerous fighter planes, strike aircraft, helicopters, and other types of aircraft. Question: What do aircraft carriers allow naval forces to accomplish?
answer:

project air power worldwide without depending on local bases


