**Core Concept**
Iodine is an essential micronutrient for thyroid hormone synthesis, and its requirement is crucial during lactation to ensure adequate milk production and optimal growth of the infant.

**Why the Correct Answer is Right**
During breastfeeding, the maternal iodine requirement increases to meet the needs of both the mother and the infant. The World Health Organization recommends an additional 50-100 μg of iodine per day during lactation. This increase is necessary to support the production of thyroid hormones, which are essential for the infant's growth and development. Iodine is also crucial for the production of lactogenic hormones, which regulate milk production in lactating women.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not reflect the increased iodine requirement during lactation.
**Option B:** This option is incorrect because it suggests that the iodine requirement remains the same during breastfeeding, which is not accurate.
**Option C:** This option is incorrect because it implies that the iodine requirement decreases during lactation, which is opposite to the actual requirement.

**Clinical Pearl / High-Yield Fact**
Adequate iodine intake during breastfeeding is essential to prevent iodine deficiency in both the mother and the infant. Iodine deficiency can lead to cretinism, a condition characterized by severe mental and physical retardation.

**Correct Answer: D. 50-100 μg per day.**