Explanation:

- Stethoscope:

- Correct Answer.

- A medical instrument used by doctors and healthcare professionals.

- Primarily for listening to internal sounds of the body, like in the heart and lungs.

- Periscope:

- An instrument typically used in submarines.

- Allows viewing over, around or through an object.

- Kaleidoscope:

- A toy consisting of mirrors and colored glass.

- Creates beautiful patterns when viewed through one end.

- Telescope:

- An instrument for observing distant objects.

- Commonly used for astronomical purposes, like viewing stars and planets.