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
Mesothelioma is - 
Select and explain. 
A. Benign, B. Rarely malignant, C. Mostly malignant, D. Always malignant
C: Mostly malignant
Answer: C: Mostly malignant 
Explanation: None