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: Unknown
Keratitis is caused by 
Select and explain. 
A. Bacteria, B. Atopy, C. Protozoa, D. All
D: All
Answer: D: All 
Explanation: Causes of keratitis
 
Infective keratitis
Bacterial
Viral
Fungal
Chlamydial
Protozoal
Spirochactal
 
Allergic keratitis
Phlyctenular keratitis
Vernal keratitis
Atopic keratitis
 
Trophic keratitis
Exposure keratitis
Neuroparalytic keratitis
Keratomalacia
Atheromatous ulcer
 
Keratitis associated with diseases of skin and mucous membrane.
Keratitis associated with systemic collagen vascular disorders.
Traumatic keratitis, which may be due to mechanical trauma, chemical trauma, thermal burns, radiations.
 
Idiopathic keratitis e.g.,

Mooren's corneal ulcer
Superior limbic keratoconjunctivitis
Superficial punctate keratitis of Thygeson