An overgrowth of scar tissue is called aSelect one:a.keloid.b.papule.c.nevus.d.vesicle.

1. Break Down the Problem

We need to determine the correct medical term that refers to an overgrowth of scar tissue from the given options.

2. Relevant Concepts

• Keloid: An overgrowth of scar tissue that occurs at the site of a healed skin injury.
• Papule: A small, raised bump on the skin that is usually less than 1 cm in diameter.
• Nevus: A mole on the skin, usually pigmented.
• Vesicle: A small fluid-filled sac or blister.

3. Analysis and Detail

From the definitions:

• Keloid directly corresponds to the description of overgrown scar tissue.
• The other options (papule, nevus, vesicle) do not relate to scar tissue growth.

4. Verify and Summarize

Given the definitions, it is clear that the term that specifically refers to an overgrowth of scar tissue is keloid.

Final Answer

The correct answer is a. keloid.