Colostrum secreted by mother is rich in:

The correct answer is Option (3) → IgA antibodies

Option (3) IgA antibodies — Correct. Colostrum, the yellowish milk of the first few days, is rich in IgA antibodies. These protect the newborn; this is passive immunity.

NCERT Extract:
Active and Passive Immunity – “When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity. … The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the infant. The foetus also receives some antibodies from their mother, through the placenta during pregnancy. These are some examples of passive immunity.”