Correct answer: B). Idiopathic
An idiopathic disease is any disease or disorder, which is caused due to an unknown cause or mechanism. When the doctor is not sure about the cause of disease, then such type of disease is called idiopathic disease. It is a Greek word, in which idios means own and pathos means suffering. It means a disease of its own kind.
Example: Acute idiopathic polyneuritis, idiopathic pulmonary fibrosis etc.