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The answer is A. The slope of the line is rise/run = 4/2 = 2.1. This means that each kilometer costs $2.10. The y-intercept is 2.1, which means that the initial fee is $2.10. So the correct statement is: The slope is 2.1. This means that each kilometer costs $2.10.
The other statements are incorrect. The slope is not 5, so each kilometer does not cost $5. The y-intercept is not 5, so the ride does not last 5 kilometers. The y-intercept is the value of the function when the input is 0, which in this case is the initial fee of $2.10.