A : The pitch of female voice is higher than the pitch of male voice .
R : Pitch distinguishes between a shrill and a grave sound .

Answer

To analyze the given statements about the pitch of male and female voices, we can break down the solution into clear steps:

### Step 1: Understand the Assertion
The assertion states that "The pitch of female voice is higher than the pitch of male voice."
- This is true because the pitch of a sound is primarily determined by the frequency of the sound waves produced. In general, females have thinner vocal cords compared to males, which leads to higher frequencies and thus a higher pitch.

**Hint:** Consider how the physical characteristics of vocal cords affect sound frequency.

### Step 2: Understand the Reason
The reason states that "Pitch distinguishes between a shrill and a grave sound."
- This statement is also true. Pitch is a perceptual property that allows us to differentiate between sounds. A shrill sound has a high pitch (like a whistle), while a grave sound has a low pitch (like a drum).

**Hint:** Think about examples of sounds that illustrate high and low pitches.

### Step 3: Evaluate the Relationship Between Assertion and Reason
Now, we need to determine if the reason provided explains the assertion.
- While both statements are true, the reason does not specifically explain why the pitch of a female voice is higher than that of a male voice. The reason talks about the general concept of pitch, while the assertion focuses on the specific comparison between male and female voices.

**Hint:** Reflect on whether the reason directly addresses the assertion or if it is a broader statement.

### Step 4: Conclusion
Based on the analysis:
- Both the assertion and the reason are true.
- However, the reason is not the correct explanation for the assertion.

Thus, the correct conclusion is that both the assertion and reason are true, but the reason does not explain the assertion.

**Final Answer:** Both assertion and reason are true, but R is not the correct explanation of A.