What is the main purpose of irrigation?

Correct answer: To provide water to crops

The direct answer is B: irrigation provides water to crops. Irrigation means supplying water to farmland by canals, wells, tubes, sprinklers or other methods when rainfall is absent, insufficient or irregular. Plants need water for seed germination, nutrient transport, photosynthesis and healthy growth. The reasoning is simple: crops are growing in soil; rainfall may not meet their water need; irrigation supplies the missing water; therefore its main purpose is to provide water to crops. Option A is wrong because darkening a field has nothing to do with watering plants. Option B is correct because supplying suitable water is exactly what irrigation does. Option C is wrong because removing soil is excavation or erosion, not irrigation. Option D is wrong because colouring grains is a processing or decoration activity, not a farming water practice. Irrigation does not mean flooding every field without control; the amount and timing should suit the crop and soil. Memory cue: irrigation means “irrigate = give water”; connect it with crops, not darkness, soil removal or grain colour.