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.
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Passage: In June 2014, state broadcaster China Central Television (CCTV) broadcast a news story further characterizing Windows 8 as a threat to national security. The story featured an interview with Ni Guangnan, who stated that operating systems could aggregate "sensitive user information" that could be used to "understand the conditions and activities of our national economy and society", and alleged that per documents leaked by Edward Snowden, the U.S. government had worked with Microsoft to retrieve encrypted information. Yang Min, a computer scientist at Fudan University, also stated that "the security features of Windows 8 are basically to the benefit of Microsoft, allowing them control of the users' data, and that poses a big challenge to the national strategy for information security." Microsoft denied the claims in a number of posts on the Chinese social network Sina Weibo, which stated that the company had never "assisted any government in an attack of another government or clients" or provided client data to the U.S. government, never "provided any government the authority to directly visit" or placed any backdoors in its products and services, and that it had never concealed government requests for client data. Question: What is the name of the Chinese social network?
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Sina Weibo

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Passage: The city of Rome had a place called the Campus Martius ("Field of Mars"), which was a sort of drill ground for Roman soldiers. Later, the Campus became Rome's track and field playground. In the campus, the youth assembled to play and exercise, which included jumping, wrestling, boxing and racing.[citation needed] Equestrian sports, throwing, and swimming were also preferred physical activities.[citation needed] In the countryside, pastimes included fishing and hunting.[citation needed] Board games played in Rome included dice (Tesserae or Tali), Roman Chess (Latrunculi), Roman Checkers (Calculi), Tic-tac-toe (Terni Lapilli), and Ludus duodecim scriptorum and Tabula, predecessors of backgammon. Other activities included chariot races, and musical and theatrical performances.[citation needed] Question: What could you also call Rome's Campus Maritus?
answer:
Field of Mars

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Passage: The immune system is a system of many biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, known as pathogens, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue. In many species, the immune system can be classified into subsystems, such as the innate immune system versus the adaptive immune system, or humoral immunity versus cell-mediated immunity. In humans, the bloodbrain barrier, bloodcerebrospinal fluid barrier, and similar fluidbrain barriers separate the peripheral immune system from the neuroimmune system which protects the brain. Question: What is the immune system?
answer:
a system of many biological structures and processes within an organism