This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
Disability was added in census from which year- 
Select and explain. 
A. 1981, B. 1991, C. 2001, D. 2011
A: 1981
Answer: A: 1981 
Explanation: First disability census was taken in 1981