Assertion:The Eustachian tube helps in equalising the pressures on either sides of the ear drum.
Reason:The Eustachian tube connects the middle ear cavity with the pharynx.

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 but reason is false.
D. If both assertion and reason are false.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Assertion**: The assertion states that the Eustachian tube helps in equalizing the pressures on either side of the eardrum. This is true because the Eustachian tube allows air to flow between the middle ear and the external environment, which helps to balance the pressure on both sides of the eardrum.

2. **Understanding the Reason**: The reason provided states that the Eustachian tube connects the middle ear cavity with the pharynx. This is also true, as the Eustachian tube indeed connects the middle ear to the nasopharynx, which is part of the throat.

3. **Analyzing the Relationship**: While both the assertion and the reason are true, we need to determine if the reason adequately explains the assertion. The reason explains the anatomical connection of the Eustachian tube but does not specifically explain how this connection leads to the equalization of pressure.

4. **Conclusion**: Since both statements are true but the reason does not provide a correct explanation for the assertion, we conclude that the answer is option B: both assertion and reason are true, but the reason is not the correct explanation for the assertion.

**Final Answer**: Option B - Both assertion and reason are true, but reason is not the correct explanation for assertion.

---