After the child birth, milk formation is controlled by prolactin/oxytocin.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which hormone controls milk formation after childbirth. The two hormones mentioned are prolactin and oxytocin.

2. **Identifying the Role of Prolactin**: Prolactin is the primary hormone responsible for milk production (lactation) in females after childbirth. It stimulates the mammary glands to produce milk.

3. **Understanding Colostrum**: After childbirth, the initial milk produced is called colostrum, which is rich in antibodies (specifically IgA) that help protect the newborn from infections.

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