Consider the following statements and choose the correct answer:
1. Roots of grasses are an excellent binding material and keep the soil intact
2. Disruption of the grass cover by the plough loosens the soil and makes it vulnerable to removal by the force of rain or strong winds
3. Tilling or grazing on slopes or semi-arid soils decreases the rate of soil erosion
4. Soil erosion is especially high in Nepal, India, China, Australia, Spain, USSR, USA and Central Africa