Which hormone is secreted by human placenta?

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the hormone secreted by the human placenta. This requires knowledge of the hormones associated with pregnancy and the role of the placenta.

2. **Identifying Key Hormones**: After fertilization, two key hormones are involved: estrogen and progesterone. These hormones play a crucial role in maintaining pregnancy.

3. **Role of the Placenta**: The placenta begins to form around the second week after fertilization. It is essential for supporting the developing embryo and fetus.

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