(a) strip farming
(b) shifting agriculture
(c) ley farming
(d) contour farming.
Ans. (c) ley farming
Sol: Ley farming is an agricultural system where the field is alternately seeded for grain and left fallow for growing hay or used for pasture. During the fallow/pasture period the soil is filled with roots of grasses and other plants. New ploughing mixes them in the soil and also increases the amount of nitrogen in the soil especially when legume forage are used. It also protects soil from erosion by maintaining constant soil coverage.