**Core Concept**
Exclusive breastfeeding refers to the practice of feeding an infant only breast milk without any additional foods or liquids, excluding vitamin and mineral supplements. This period is crucial for the infant's growth, development, and immune system maturation.

**Why the Correct Answer is Right**
The World Health Organization (WHO) recommends exclusive breastfeeding for the first six months of life. During this period, breast milk provides optimal nutrition, including proteins, fats, carbohydrates, vitamins, and minerals necessary for the infant's growth and development. Additionally, breast milk contains antibodies that help protect the infant from infections and diseases. The American Academy of Pediatrics (AAP) also supports exclusive breastfeeding for the first six months, with continued breastfeeding as complementary foods are introduced, up to 12-24 months of age.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not align with the current recommendations from the WHO and AAP. Exclusive breastfeeding for the first four months may not provide sufficient nutrition for the infant's growth and development.
**Option B:** This option is incorrect because it suggests a longer duration than recommended by the WHO and AAP. Exclusive breastfeeding beyond six months may not provide optimal nutrition for the infant, and may also lead to nutrient deficiencies in the mother.
**Option C:** This option is incorrect because it does not specify a clear duration, making it an ambiguous and unreliable choice.

**Clinical Pearl / High-Yield Fact**
It is essential to note that exclusive breastfeeding should be continued until the infant is developmentally ready for complementary foods, which is typically around six months of age. However, the decision to introduce complementary foods should be based on the infant's individual developmental readiness, rather than a specific age.

**Correct Answer: D. Six months. Exclusive breastfeeding should be done till six months.**