A person starts at 9:00 in the morning, and walks a total of 300km at 12:00 and then continues walking after a 45-minute break. At the end of the journey，it is 18:45 in the afternoon, the speed is 80 km/h in the afternoon. What is the average speed of the whole trip (not counting the noon break)?
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A80km/h
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B90km/h
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C95km/h
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D260/3 km/h
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E97km/h
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正确答案: D