**Core Concept**
The World Health Organization recommends exclusive breastfeeding for the first six months of life to ensure optimal nutrition and health benefits for infants.

**Why the Correct Answer is Right**
The American Academy of Pediatrics (AAP) and the World Health Organization (WHO) both recommend exclusive breastfeeding for the first six months of life. This period allows infants to receive all the necessary nutrients, antibodies, and immunoglobulins from breast milk, which helps to protect them against infections and promotes healthy growth and development. Exclusive breastfeeding during this period also supports the development of a healthy gut microbiome and reduces the risk of respiratory and ear infections.

**Why Each Wrong Option is Incorrect**
**Option A:** Four months is too early to stop exclusive breastfeeding, as infants still require the nutrients and antibodies present in breast milk during this period.
**Option C:** Twelve months is longer than the recommended period for exclusive breastfeeding, and may lead to an inadequate diet and potential nutritional deficiencies.
**Option D:** Twenty-four months is excessively long, and most infants will have already transitioned to solid foods and may be consuming other sources of nutrition.

**Clinical Pearl / High-Yield Fact**
The "6-8-10" rule is a useful mnemonic for pediatricians: breastfeed exclusively for 6 months, introduce solid foods around 8 months, and wean by 10-12 months.

✓ Correct Answer: B. 6 months