None of the provided responses represent the correct ratio for the constant of proportionality. The constant of proportionality can be found by dividing the number of pages read by the time taken to read them.
To find the constant of proportionality for Ruth's reading speed, we can divide the number of pages read by the time taken to read them for each data point:
For the first data point: 15 pages / 12 hours = 1.25 pages per hour
For the second data point: 30 pages / 1 hour = 30 pages per hour
For the third data point: 45 pages / 112 hours ≈ 0.4018 pages per hour
For the fourth data point: 60 pages / 2 hours = 30 pages per hour
From these calculations, we can see that the ratio for the constant of proportionality is 30 pages read per hour. Therefore, the correct answer is none of the provided responses.