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
Age related dementia has been associated with increased levels of 
Select and explain. 
A. Homocysteine, B. Cysteine, C. Tourine, D. Methionine
A: Homocysteine
Answer: A: Homocysteine 
Explanation: 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