The correct answer is option 3, Wisdom-teeth. Vestigial organs are anatomical structures that have lost their original function over the course of evolution.

Option 1, Eye-brow: Eyebrows are not considered vestigial organs as they serve to protect our eyes from sweat and debris.

Option 2, Collar-bone: The collarbone, also known as the clavicle, plays an important role in supporting the shoulder and arm. It is not a vestigial organ.

Option 4, Nails: Nails are formed by a protein called keratin and serve various purposes such as protecting the fingertips and enhancing gripping abilities. They are not vestigial organs.

Wisdom-teeth, option 3, are the third set of molars that typically develop in late teens or early twenties. They were useful in our ancestors for chewing tough plant material, but due to changes in diet and jaw size, they are now often unnecessary and can sometimes cause dental issues. Therefore, wisdom teeth are considered vestigial organs.