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: Medicine
Fredrich's ataxia is caused by which type of mutation - 
Select and explain. 
A. Point mutation, B. Expanded trinucleotide repeat, C. Missense mutation, D. Inversion
B: Expanded trinucleotide repeat
Answer: B: Expanded trinucleotide repeat 
Explanation: None