Generally speaking, the meaning of farming refers to the mechanical operation of soil in order to improve crop growth conditions before planting or during growth. The purpose of farming is threefold: (1) improving soil structure; (2) turning crop residues Stubble and organic fertilizer are buried and incorporated into the soil: (3) weeds and other unwanted plants are removed. According to the above definition, which of the following options is farming? ['ken topsoil after snowing.', ' a drainage ditch beside the wheat field.', 'Growing green manure crops in farmland.', 'Spray pesticides to kill pests.']