Concept:Diagnostic tests identify students' learning weaknesses and strengths to guide remedial actions.Explanation:These tests uncover persistent or recurring learning difficulties not resolved by formative evaluation.They pinpoint specific errors and their causes, helping teachers adjust instruction.The main goal is to determine learning problems and plan targeted remedies.Thus, diagnostic tests are used to find out students' deficiencies with a view to plan remedy.Answer:A. find out deficiencies of the students with a view to plan remedy.