Life begin in all sexually reproducing organisms as a

Options

A. single-celled zygote
B. double-celled zygote
C. haploid zygote
D. haploid gametes.

Explanation

### Step-by-Step Solution:

1. **Understanding Sexual Reproduction**: Sexual reproduction involves the fusion of male and female gametes. The male gamete (sperm) and the female gamete (egg) come together during a process called fertilization.

2. **Fertilization Process**: During fertilization, the sperm and egg unite to form a zygote. This is a crucial step in sexual reproduction as it marks the beginning of a new organism's life.

3. **Formation of Zygote**: The zygote is the initial cell formed when the male and female gametes fuse. At this stage, the zygote is a single-celled structure.

4. **Development of the Zygote**: After its formation, the zygote undergoes a series of cell divisions and developmental processes to eventually form an embryo. This marks the transition from a single cell to a multicellular organism.

5. **Conclusion**: Therefore, in all sexually reproducing organisms, life begins as a single-celled zygote formed from the fusion of male and female gametes.

### Final Answer:
Life begins in all sexually reproducing organisms as a **single-celled zygote**.

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