Which of the following involves tissue that is separated from its base and lost without adequate attachment?

Avulsion refers to an injury where tissue is forcibly separated from its base or point of attachment. This type of injury can result in the complete or partial tearing away of skin, muscle, or other bodily structures. It is distinct in that it typically involves a significant disruption of the underlying tissue, which may lead to complications such as severe bleeding, infection, and the need for surgical intervention to repair the damage.

In the context of the other options, an abrasion involves the scraping away of the skin's surface, a laceration refers to a jagged or irregular tear in the flesh, and a contusion is a bruise resulting from damage to blood vessels without breaking the skin. These injuries do not involve the complete separation of tissue from its base, making avulsion the correct answer in this scenario.