Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: In order to make a line graph showing the rate of erosion on the banks of a river during a week-long flood, the y-axis should be labeled as the width of the river bank, in meters. The best label for the x-axis is time, in
hours, days or weeks?