Erosion causes a river to become deeper and wider.
Erosion is the work of wind, water, and time.
The work of wind, water, and time causes a river to become deeper and wider.
The work of what causes a river to become deeper and wider?

1: looseness of dirt or compost
2: just time
3: Veins and arteries.
4: just wind
5: Physical weathering
6: The area was once underwater
7: just water
8: wind, water, and time