When water flows across farm land, some soil is washed away, resulting in erosion. An experiment was conducted to investigate the effect of the rate of water flow (liters per second) on the amount of soil (kilograms) washed away. The data are given in the following table.
Flow rate
.31
.85
1.26
2.47
3.75
Eroded soil
.82
1.95
2.18
3.01
6.07

The association between flow rate and amount of eroded soil is
A. positive.
B. negative.
C. neither positive nor negative.
D. impossible to determine since both variables are categorical.