Assertion :- Each chromatid is attached with two spindle fibres during S-phase :-
Reason :- During Anaphse-I each chromosome is found in bivalent form.

Options

A. If both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. If both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion & Reason are false.

Answer

To analyze the assertion and reason provided in the question, we will evaluate each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states: "Each chromatid is attached with two spindle fibers during S-phase."
- In the S-phase of the cell cycle, DNA replication occurs, resulting in the formation of sister chromatids. However, the attachment of spindle fibers to chromatids occurs during the later stages of cell division, specifically during metaphase and anaphase, not during S-phase.
- Therefore, the assertion is **incorrect**.

2. **Understanding the Reason:**
- The reason states: "During Anaphase-I, each chromosome is found in bivalent form."
- In meiosis, the bivalent form (where homologous chromosomes are paired) is observed during prophase I and metaphase I. By anaphase I, the homologous chromosomes have already separated, and each chromosome consists of two sister chromatids. Thus, they are no longer in bivalent form at this stage.
- Therefore, the reason is also **incorrect**.

3. **Conclusion:**
- Since both the assertion and the reason are incorrect, we conclude that the answer to the question is: **Both assertion and reason are false.**