Here is a question about this article: In the Mexico City airport, the government engaged in an extensive restructuring program that includes the addition of a new second terminal, which began operations in 2007, and the enlargement of four other airports (at the nearby cities of Toluca, Queretaro, Puebla and Cuernavaca) that, along with Mexico City's airport, comprise the Grupo Aeroportuario del Valle de Mexico, distributing traffic to different regions in Mexico. The city of Pachuca will also provide additional expansion to central Mexico's airport network. Mexico City's airport is the main hub for 11 of the 21 national airline companies.
What is the answer to this question: How many national airlines are there in Mexico?
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So... 21

Here is a question about this article: The original city council line-up of 14 members (nine district-based and five at-large positions) was based on a U.S. Justice Department mandate which took effect in 1979. At-large council members represent the entire city. Under the city charter, once the population in the city limits exceeded 2.1 million residents, two additional districts were to be added. The city of Houston's official 2010 census count was 600 shy of the required number; however, as the city was expected to grow beyond 2.1 million shortly thereafter, the two additional districts were added for, and the positions filled during, the August 2011 elections.
What is the answer to this question: What population figure needs to be passed to add at large council members?
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So... 2.1 million

Here is a question about this article: Retrotransposons can be transcribed into RNA, which are then duplicated at another site into the genome. Retrotransposons can be divided into Long terminal repeats (LTRs) and Non-Long Terminal Repeats (Non-LTR).
What is the answer to this question: What kind of genetic material can be produced from retrotransposons?
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So...
RNA