Phonoreceptors occur in

Options

A. Skin
B. Middle ear
C. Tympanum
D. Internal ear.

Answer

**Step-by-Step Solution:**

1. **Understanding Phonoreceptors**: Phonoreceptors are specialized sensory receptors that detect sound and vibrations. They play a crucial role in the auditory system.

2. **Analyzing the Options**:
- **Option A: Skin**: The skin contains different types of receptors, such as thermoreceptors for temperature detection, but it does not have phonoreceptors. Therefore, this option is incorrect.
- **Option B: Middle Ear**: The middle ear is responsible for transmitting sound vibrations but does not contain phonoreceptors. Thus, this option is also incorrect.
- **Option C: Tympanum**: The tympanum, or tympanic cavity, is part of the middle ear and similarly does not contain phonoreceptors. This option is incorrect as well.
- **Option D: Internal Ear**: The internal ear (or inner ear) contains the cochlea and other structures that house the phonoreceptors responsible for detecting sound. This makes this option the correct answer.

3. **Conclusion**: After evaluating all the options, the correct answer is that phonoreceptors occur in the **internal ear**.

**Final Answer**: D. Internal Ear

---