Concept:Flood irrigation is a method where the field is flooded with water, suitable for crops that grow well under such conditions.Explanation:Among the options, swamp rice (paddy) is the crop that requires standing water for most of its growth.It is commonly cultivated in flooded fields, especially in lowland areas.Watermelon, oil palm, and coconut do not need continuous flooding and therefore are not cultivated using flood irrigation.Answer:B. swamp rice