The following are multiple choice questions (with answers) about medical knowledge.   **Question:** The analytical study where population is the unit of study is   (A) Cross-sectional   (B) Ecological   (C) Case-control   (D) Cohort study
['(B) Ecological <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Cross-sectional \n (B) Ecological \n (C) Case-control \n (D) Cohort study <> possible answers', '  The analytical study where population is the unit of study is <> context@']