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: E 122nd Street runs four blocks (2,250 feet (690 m)) west from the intersection of Second Avenue and terminates at the intersection of Madison Avenue at Marcus Garvey Memorial Park. This segment runs in East Harlem and crosses portions of Third Avenue, Lexington, and Park (Fourth Avenue). Question: What is another name for Fourth Avenue?
Example Output: Park

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: Biggeri and Mehrotra have studied the macroeconomic factors that encourage child labour. They focus their study on five Asian nations including India, Pakistan, Indonesia, Thailand and Philippines. They suggest that child labour is a serious problem in all five, but it is not a new problem. Macroeconomic causes encouraged widespread child labour across the world, over most of human history. They suggest that the causes for child labour include both the demand and the supply side. While poverty and unavailability of good schools explain the child labour supply side, they suggest that the growth of low-paying informal economy rather than higher paying formal economy is amongst the causes of the demand side. Other scholars too suggest that inflexible labour market, sise of informal economy, inability of industries to scale up and lack of modern manufacturing technologies are major macroeconomic factors affecting demand and acceptability of child labour. Question: Supply and what else causes child labour to still exist today?
Example Output:
demand