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
Shanti, aged 27 yrs presented with complaints of difficulty in reading near print. There is ptosis and diplopia in all directions. She is having- 
Select and explain. 
A. III CN palsy, B. Myasthenia gravis, C. Presbyopia, D. VI CN palsy
B: Myasthenia gravis
Answer: B: Myasthenia gravis 
Explanation: Amongst the given options ptosis can be caused by 3rd nerve palsy and myasthenia gravis. However, in 3rd nerve palsy diplopia will not occur on Down & out gaze (due to sparing of SO and LR) while in myasthenia gravis, diplopia will occur in all directions.