Why are the articles there?

0I was looking at the OWL Online Writing Lab for an exercise on articles and in it, it had this (I chose few sentences from the exercise to ask this question):02br
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01i00A horse knows when he is going to race ... Sometimes he doesn't know when 01u00the02u00 starting gate flies open and 01u00the02u00 track is before him... 01u00The02u00 exercise boy, watching the owner's favorite jockey riding the horse he had exercised day after day, says ...02i02br
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00The first 01i00the02i00 seems to be there because a previous sentence said that the horse was led to the grandstand and 01i00the 02i00before grandstand was there because it is obvious from the circumstances or situations; similar to when we say "John is washing his hands in 01u00the02u00 bathroom."02br
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00Would you say the first and second "thes" are there because they too are obvious due to the circumstances? If yes, then how would you explain the existence of the third 01i00the 02i00before "exercise boy"?0-