Assertion: on stimulation, a muscle cell releases calcium ions `(Ca^(2+))` from sarcoplasmic reticulum.
Reason: By reacting with a protien complex, `Ca^(2+)` uncover active sites on the actin filaments.

Options

A. If both assertion and reason are ture and reason is the corect explanation of assertion
B. If both assertion and reason are ture but reson is not the correct explanation of assertion
C. If assertion is true reason is false
D. If both assertion and reason are false

Explanation

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that on stimulation, a muscle cell releases calcium ions (Ca²⁺) from the sarcoplasmic reticulum. This is true because the sarcoplasmic reticulum serves as a storage site for calcium ions in muscle cells. When a muscle cell receives a signal (action potential), it triggers the release of these ions.

**Hint**: Recall the role of the sarcoplasmic reticulum in muscle contraction.

2. **Understanding the Reason**: The reason states that calcium ions react with a protein complex to uncover active sites on the actin filaments. This is also true. Calcium ions bind to troponin, a protein associated with actin, which causes a conformational change that exposes the active sites on actin filaments, allowing myosin to bind.

**Hint**: Think about how calcium ions interact with troponin and the role of this interaction in muscle contraction.

3. **Evaluating the Relationship**: While both the assertion and reason are true, the reason does not directly explain why calcium ions are released from the sarcoplasmic reticulum. Instead, it describes the subsequent action of calcium ions after their release.

**Hint**: Consider whether the reason provides a direct explanation for the assertion or if it merely describes a related process.

4. **Conclusion**: Therefore, the correct answer is that both the assertion and reason are true, but the reason does not explain the assertion.

**Hint**: Review the definitions of assertion and reason in the context of logical reasoning questions.

### Final Answer:
Both the assertion and reason are true, but the reason does not explain the assertion.