This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Linea alba is 
Select and explain. 
A. A type of frictional hyperkeratosis that appears as a linear white line in buccal mucosa., B. Usually present as ulcers, C. Traumatic implantation of amalgam particles into mucosa., D. Caused by a chemical in tobacco smoke that stimulates melanin production.
A: A type of frictional hyperkeratosis that appears as a linear white line in buccal mucosa.
Answer: A: A type of frictional hyperkeratosis that appears as a linear white line in buccal mucosa. 
Explanation: None