The correct answer is (a), (c), (d). The crop period is the number of days between sowing and harvesting. Its not related to irrigation. Delta is the total depth of water required by the plants throughout the base period. Duty is the hectare land covered by 1m3/sec (cumec) stream discharge during the base period. The intensity of irrigation is the percentage of culturable command area irrigated in the given time period. Mistake PointsCrop period = Number of days between sowing and harvestingBase period = Number of days between the first and last watering of the crop