This table shows the cost of renting a kayak.

The cost of renting a kayak is represented by the equation $y=8x+5$.,
where $x$ represents the number of hours.

What does the slope of the equation represent
A. the cost of renting a kayak for 8 hours
B. the cost of renting a kayak for 5 hours
C. the total cost of the rental
D. the cost increase for each hour of rental