Explanation

Colostrum is the thick, yellowish first milk produced in the initial days after childbirth. It is exceptionally rich in antibodies, especially secretory IgA, along with leukocytes and growth factors, giving the newborn its first immune protection. Ordinary breast milk and transitional milk come later and are less concentrated in immune factors, and 'mineralized milk' is not a recognised category. Hence colostrum is the correct answer.