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: Ophthalmology
5% guanethidine is used for 
Select and explain. 
A. Ptosis, B. Neuro-paralytic keratitis, C. Thyrotoxic ophthalmopathy, D. Homer's syndrome
C: Thyrotoxic ophthalmopathy
Answer: C: Thyrotoxic ophthalmopathy 
Explanation: C. i.e. Thyrotoxic opthalmopathy