Assertion: Tetany is rapid spasm in muscle.
Reason: Tetany is usually caused by an increases in the blood calcium level.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason 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 "Tetany is a rapid spasm in muscle." This is true. Tetany refers to a condition characterized by involuntary muscle contractions or spasms.

2. **Understanding the Reason**: The reason provided is that "Tetany is usually caused by an increase in the blood calcium level." This statement is false. Tetany is actually caused by a decrease in blood calcium levels, a condition known as hypocalcemia.

3. **Analyzing the Relationship**: Since the assertion is true (tetany is indeed a rapid spasm in muscles), but the reason is false (it is caused by low, not high, calcium levels), we conclude that the assertion and reason do not support each other.

4. **Selecting the Correct Option**: Based on the analysis, the correct answer is that the assertion is true, but the reason is false. This corresponds to option C.

**Final Answer**: Assertion is true but reason is false (Option C).

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