This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': 'Age related dementia has been associated with increased levels of \nSelect and explain. \nA. Homocysteine, B. Cysteine, C. Tourine, D. Methionine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Identification of modifiable risk factors provides a crucial approach to the prevention of dementia.. The findings are consistent with moderately raised plasma total homocysteine (>11 mmol/L), which is common in the elderly, being one of the causes of age-related cognitive decline and dementia Ref Harrison20th edition pg 2445', 'role': 'assistant'}]