This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
"Incidence" is defind as- 
Select and explain. 
A. Number of new cases occurring in a defined population, B. Total cases (new + old) occurring in a defined population, C. Number of exposed developing the disease in a defined population, D. None of the above
D: None of the above
Answer: D: None of the above 
Explanation: Incidence is defined as the number of new cases occurring in a defined population during a specified period of time. It can also refer to a new spell or episodes of disease arising in a given period of time per 1000 population. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 68