In the larynx, which of the following is a thin elastic cartilaginous flap?
(a) Thyroid
(b) Soundbox
(c) Glottis
(d) Epiglottis

Options

A. Thyroid
B. Soundbox
C. Glottis
D. Epiglottis

Answer

To solve the question, "In the larynx, which of the following is a thin elastic cartilaginous flap?" we need to analyze the options provided:

1. **Understanding the structure of the larynx**: The larynx is an important part of the respiratory system, located in the throat. It is responsible for sound production and also plays a role in protecting the airway during swallowing.

2. **Evaluating the options**:
- **(a) Thyroid**: The thyroid is a large cartilage that forms the front part of the larynx, but it is not a flap and is not elastic.
- **(b) Soundbox**: This term is not a specific anatomical structure; it generally refers to the larynx as a whole but does not identify a specific flap.
- **(c) Glottis**: The glottis is the opening between the vocal cords in the larynx, but it is not a flap.
- **(d) Epiglottis**: The epiglottis is a thin, elastic cartilaginous flap that covers the glottis during swallowing, preventing food from entering the windpipe.

3. **Conclusion**: Based on the evaluation, the correct answer is **(d) Epiglottis**. It is the thin elastic cartilaginous flap that plays a crucial role in protecting the airway.

### Final Answer:
**(d) Epiglottis**