Final answer:
The slope of the relationship between time and the length of a candle burning at a constant rate should be negative, indicating a decrease in candle height as time increases. This would result in a graph showing a straight line with a negative slope.
Step-by-step explanation:
The question you've asked pertains to the relationship between time and the length of the candle as it burns. When a candle burns, it gets shorter over time at a constant rate. In this case, because the candle is burning at a constant rate of 2.5cm/h, the height of the candle is decreasing steadily as time progresses. Therefore, the slope of this relationship should be negative because as time increases, the height of the candle decreases. If we were to graph this relationship with time on the horizontal axis and candle height on the vertical axis, we would see a straight line with a negative slope. When comparing different types of slopes: a positive slope means that as one variable increases, the other variable also increases; a negative slope indicates that as one variable increases, the other variable decreases; and a zero slope indicates that there is no change in the second variable as the first one changes, which gives us a horizontal line.