Final answer:
The thick yellow fluid from nipples is called colostrum, which is most commonly found in parous women who have previously given birth. Colostrum is rich in proteins and antibodies, providing the newborn with initial protection against diseases.
Step-by-step explanation:
The thick yellow fluid from nipples is called colostrum and is most common in parous women. The correct answer to fill in the blank is option a) Colostrum.
Colostrum is a form of breast milk produced by the mammary glands in late pregnancy and the few days after giving birth. It is high in protein, contains less fat and glucose than mature breast milk, and includes antibodies to protect the newborn against disease. In parous women, those who have given birth previously, the nipples may leak colostrum during the final weeks of pregnancy, and it is the first substance to be secreted before mature breast milk is produced.
In contrast to prolactin, which is the hormone involved in the synthesis of milk, or lactose, which is a sugar found in milk, or serous fluid, which is a component of bodily fluids, colostrum is the only option that represents the thick yellow fluid produced by the nipples as described.