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
Which glands does not contribute to Aqueous layer of tear film 
Select and explain. 
A. Lacrimal, B. Accessory lacrimal, C. Wolfring, D. Zeis
D: Zeis
Answer: D: Zeis 
Explanation: Zeis contributes to oil layer.