Concept:Diagnostic tests are designed to identify specific learning gaps and errors in a student's understanding.
Explanation:A teacher uses diagnostic tests during or after a chapter to pinpoint where learners make mistakes.
These tests help locate problem areas and weaknesses in a child's grasp of a topic.
They also reveal the underlying causes of slow learning or frequent errors.
Based on these findings, the teacher can plan remedial teaching to improve learning quality.
Thus, the main purpose of a diagnostic test is to know the gaps in a child's understanding.
Answer:A. Knowing gaps in child's understanding