Explanation:

Assertion A states that breast-feeding during the initial period of infant growth is recommended by doctors to bring up a healthy baby. This statement is indeed correct. Breast-feeding is universally recommended by health professionals because mother's milk contains the perfect balance of nutrients essential for the newborn's growth and development. Additionally, breastfeeding promotes better health outcomes for the mother and infant, strengthening the immune system of the baby.

Reason R explains that colostrum, the first form of milk produced immediately following the delivery of the newborn, contains several antibodies absolutely essential to develop resistance for the newborn baby. This statement is also correct. Colostrum is rich in immunoglobulins, particularly IgA, which provide passive immunity to the baby by forming a protective layer in the baby's intestine, thereby preventing infection.

Since both Assertion A and Reason R are correct, and Reason R directly explains why breastfeeding is beneficial — particularly highlighting the role of colostrum in providing immunity which is crucial for the newborn's health, the correct option herein is:

Option A: Both A and R are correct and R is the correct explanation of A.