Read the passage carefully and choose the correct answer. Crop rotatio

Read the passage carefully and choose the correct answer. Crop rotation is the practice of growing different types of crops in the same field in sequential seasons to avoid a decrease in soil fertility, as growing the same crop epeatedly in the same place eventually depletes the soil of various nutrients. Crop rotation helps to balance the fertility demands of various crops. By crop rotation farmers can keep their fields under continuous production, without the need to let them lie fallow, and reducing the need for artificial fertilizers, both of which can be expensive. In subsistence farming, it also makes good nutritional sense to grow beans and grain at the same time in different fields. Crop rotation is also used to control pests and diseases that can become established in the soil over time. Plants within the same family tend to have similar pests and pathogens. By regularly changing the planting location, the pest cycles can be broken or limited. This principle is of particular use in organic farming, where pest control may be achieved without synthetic pesticides. The choice and sequence of rotation crops depends on the nature of the soil, the climate, and precipitation which together determine the type of plants that may be cultivated. Other important aspects of farming such as crop marketing and economic variables must also be considered when choosing a crop rotation. Crop rotation was already mentioned in the Roman literature, and referred to by great civilizations in Africa and Asia. From the end of the Middle Ages until the 20th century, the three-year rotation was practised by farmers in Europe.    Question 36: Farmers who practice crop rotation ____.