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: A physical USB device may consist of several logical sub-devices that are referred to as device functions. A single device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function). This kind of device is called a composite device. An alternative to this is compound device, in which the host assigns each logical device a distinctive address and all logical devices connect to a built-in hub that connects to the physical USB cable. Question: What are logical sub-devices referred to as?

A: device functions
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Q: Passage: Most migrations begin with the birds starting off in a broad front. Often, this front narrows into one or more preferred routes termed flyways. These routes typically follow mountain ranges or coastlines, sometimes rivers, and may take advantage of updrafts and other wind patterns or avoid geographical barriers such as large stretches of open water. The specific routes may be genetically programmed or learned to varying degrees. The routes taken on forward and return migration are often different. A common pattern in North America is clockwise migration, where birds flying North tend to be further West, and flying South tend to shift Eastwards. Question: What obsticals will migrating birds avoid?

A: large stretches of open water
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Q: Passage: Initially, the station's range was officially a 40 kilometres radius of the Alexandra Palace transmitterin practice, however, transmissions could be picked up a good deal further away, and on one occasion in 1938 were picked up by engineers at RCA in New York, who were experimenting with a British television set. Question: How far from its studio could the BBC's broadcast originally reach?

A:
40 kilometres
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