Step 1: Iodine requirement rises in pregnancy and lactation because the mineral is needed for maternal and fetal/infant thyroid hormone synthesis. Step 2: The RDA of iodine for a lactating woman is 250 micrograms per day, making option d the correct answer. Step 3: For comparison, the RDA in pregnancy is 220 micrograms per day, and 150 micrograms per day is the requirement for a non-pregnant non-lactating adult. Step 4: So option b (220) is the pregnancy value, option a (150) is the normal adult value, and option c (100) is below requirement; the lactation-specific figure is 250 micrograms per day.