<s>[INST] context: There are mainly two types of cancer registry functional in India. HOSPITAL BASED REGISTRIES: The hospital-based registry indudes all patients treated by a paicular institution, whether inpatients or out-patients. Registries should collect uniform minimum set of data recommended in the '"WHO Handbook for Standardized Cancer Registers". If there is a long-term follow-up of patients, hospital-based registries can be of considerable value in the evaluation of diagnostic and treatment programmes. Since hospital population will always be a selected population, the use of these registries for epidemiological purposes is thus limited. POPULATION-BASED REGISTRIES : A right step is to set up a "hospital-based cancer registry" and extend same to a ''population-based cancer registry". The role is to cover the complete cancer situation in a given geographic area. The optimum size of base population for a population based cancer registry is in the range of 2-7 million. The data from such registries alone can provide the incidence rate of cancer and serve as a useful tool for initiating epidemiological enquiries into causes of cancer, surveillance of time trends, and planning and evaluation of operational activities in all main areas of cancer control. [/INST] question: Base population for a population based cancer registry is:- | options: A: 1-2 million B: 1-3 million C: 1-5 million D: 2-7 million | answer: D </s>