Given the task definition and input, reply with output. You are given a short paragraph, a question and two choices to answer from. Choose the correct answer based on the paragraph and write the answer(not the key).

Paragraph: Water flowing over a steeper slope moves faster and causes more erosion.
Question: Mona is a scientist studying erosion at a university. She is observing a river. If she starts taking erosion measurements at the mouth of the river and moves up to the head of the river, what will she find happens as the slope gets less steep?
Choices: A)erosion decreases
B)erosion increases
erosion decreases