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
Brown skin cornea is seen in -a) Siderosisb) Mustard gas exposurec) Chalcosisd) Argyrosis 
Select and explain. 
A. ac, B. bc, C. ad, D. b
A: ac
Answer: A: ac 
Explanation: Brown discoloration of cornea may be seen in :-


Siderosis (Iron deposition)     
Chalcosis (copper deposition) : KF rings           
Drugs : Phenothiazines vii) Kyrle disease
Chrysiasis (gold deposition)
Blood staining
Benzoquinone, hydroquinine


Argyrosis (silver deposition) causes slate gray discoloration.
I am not sure about option b