The life of a human being begins as a single celled ________

Options

A. zygote
B. embryo
C. fetus
D. egg

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the initial stage of human life, specifically what it begins as when it is a single-celled organism.

2. **Identifying the Options**: The options provided are Zygote, Embryo, Fetus, and Egg. We need to analyze each of these terms to determine which one represents the single-celled stage of human life.

3. **Analyzing the First Option - Zygote**: A zygote is formed when a sperm cell fertilizes an egg cell. This fertilized egg is a single-celled organism and marks the very beginning of human development.

4. **Analyzing the Second Option - Embryo**: An embryo is the stage that follows the zygote. It represents the early development of a multicellular organism and is not a single-celled entity.

5. **Analyzing the Third Option - Fetus**: A fetus is the term used for the developing human after the embryonic stage. It is not single-celled; rather, it is a more advanced stage of development.

6. **Analyzing the Fourth Option - Egg**: An egg refers to the female gamete (ovum) and is not a stage of development but rather the cell that gets fertilized to form a zygote.

7. **Conclusion**: Based on the analysis, the correct answer to the question is that the life of a human being begins as a single-celled **Zygote**.

**Final Answer**: The life of a human being begins as a single-celled **Zygote**.

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