Concept:Visual aids are teaching tools that rely only on the sense of sight. They help students understand concepts through images, diagrams, and written text.
Explanation:Visual aids are seen but not heard. Examples include line diagrams, charts, blackboard drawings, slides, posters, and flashcards.
Option A lists line diagram, instruments (like drawing tools), black-board, and slides – all are purely visual aids.
Option B has radio (audio) and TV (audio-visual) – not purely visual.
Option C includes radio and TV – again not only visual.
Option D includes tape recorder (audio) – so it is not a visual aid.
Therefore, only option A contains only visual aids.
Answer:A. Line diagram, Instruments, Black-board, Slides