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.

[Q]: Passage: Maximilian was deeply dissatisfied with General Bazaine's decision to abandon the state capital of Chihuahua and immediately ordered Agustin B. Billaut to recapture the city. On December 11, 1865, Billaut with a force of 500 men took control of the city. By January 31, 1866 Billaut was ordered to leave Chihuahua, but he left behind 500 men to maintain control. At the zenith of their power, the imperialist forces controlled all but four states in Mexico; the only states to maintain strong opposition to the French were: Guerrero, Chihuahua, Sonora, and Baja California. Question: In which year did Billaut capture Chihuahua?
[A]: 1865

[Q]: 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?
[A]: the complex "two-signal" activation

[Q]: Passage: The last opus number that Chopin himself used was 65, allocated to the Cello Sonata in G minor. He expressed a deathbed wish that all his unpublished manuscripts be destroyed. At the request of the composer's mother and sisters, however, his musical executor Julian Fontana selected 23 unpublished piano pieces and grouped them into eight further opus numbers (Opp. 6673), published in 1855. In 1857, 17 Polish songs that Chopin wrote at various stages of his life were collected and published as Op. 74, though their order within the opus did not reflect the order of composition. Question: How many unfinished pieces did Julian Fontana make into eight more opus numbers?
[A]:
23