During __ the sister chromatids are lined up at the equator.

Options

A. prophase I
B. prophase II
C. metaphase I
D. metaphase II

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
- The question asks during which phase of cell division the sister chromatids are aligned at the equator of the cell.

2. **Identifying the Phases of Cell Division:**
- The cell cycle includes several phases: Interphase, Prophase, Metaphase, Anaphase, and Telophase. We need to focus on the stages of mitosis where the alignment of sister chromatids occurs.

3. **Analyzing Mitosis:**
- In mitosis, the relevant phases are:
- **Prophase:** Chromosomes condense and become visible, but they are not yet aligned.
- **Metaphase:** The chromosomes line up at the cell's equatorial plane (metaphase plate).
- **Anaphase:** Sister chromatids are pulled apart towards opposite poles of the cell.
- **Telophase:** Chromatids reach the poles and begin to de-condense.

4. **Focusing on Metaphase:**
- During metaphase, spindle fibers attach to the kinetochores of the chromosomes, and the sister chromatids are aligned along the metaphase plate at the equator of the cell.

5. **Conclusion:**
- Therefore, the correct answer to the question is "Metaphase."

**Final Answer:**
During **Metaphase**, the sister chromatids are lined up at the equator.

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