This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
Which is the only drug effective in improving EDSS in multiple sclerosis? 
Select and explain. 
A. Methotrexate, B. Fingolimod, C. Glatiramer acetate, D. Natalizumab
D: Natalizumab
Answer: D: Natalizumab 
Explanation: The statement only drug effective in improving EDSS seems to be wrong because many drugs have shown to reduce disease severity on EDSS scores. Expanded disability status score(EDSS) is a scoring system for MS where high score means worsening neurological dysfunction. Maximum reduction in EDSS is seen in natalizumab group. Ref :Harrisons 18th ed.