Yellowish fluid which contains Ig A antibody and protects in initial day of infant is :-

Answer

**Step-by-Step Solution:**

1. **Identify the Yellowish Fluid**: The question asks for a yellowish fluid that contains IgA antibodies and protects infants in their initial days.

2. **Understand the Context**: This fluid is produced during the early stages of lactation, specifically right after childbirth.

3. **Recognize the Characteristics**: The fluid in question is known for its high concentration of antibodies, particularly immunoglobulin A (IgA), which plays a crucial role in the immune defense of the newborn.

4. **Name the Fluid**: The yellowish fluid that fits this description is called "colostrum."

5. **Explain the Function**: Colostrum is important because it provides the initial immune response for the infant, helping to protect against infections and diseases during the first few days of life.

6. **Conclude the Answer**: Therefore, the answer to the question is colostrum.

---