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
Muscle to be affected commonly in thyroid ophthalmopathy is: 
Select and explain. 
A. Superior rectus, B. Inferior rectus, C. Superior oblique, D. Inferior oblique
B: Inferior rectus
Answer: B: Inferior rectus 
Explanation: Ans. B: Inferior rectus In moderate active thyroid ophthalmopathy, the signs and symptoms are persistent and increasing and include myopathy. The inflammation and edema of the extraocular muscles lead to gaze abnormalities. The inferior rectus muscle is the most commonly affected muscle and patient may experience veical diplopia on upgaze and limitation of elevation of the eyes due to fibrosis of the muscle.