This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy, Development and clinical examination, Subject name: Ophthalmology
Which of the following is contrast sensitivity testing cha? 
Select and explain. 
A. Pellirobsons, B. Snellen type cha, C. Regan cha, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Contrast sensitivity is affected by various factors like age, refractive errors, glaucoma, amblyopia, diabetes, optic nerve diseases and lenticular changes. Fuher, contrast sensitivity may be impaired even in the presence of normal visual acuity. Reference : A K KHURANA COMPREHENSIVE OPHTHALMOLOGY, Edition4 ,page-17