Study the flow chart given below. What can be placed at P, Q, R and S?

• A. PQRSWindow paneCeramic  tileIron rodSpectacle lens               
• B. PQRSIron rodRubber bandCeramic  tileSpectacle lens               
• C. PQRSIron rodRubber bandWindow paneCeramic tile               
• D. PQRSCeramic tileWindow paneRubber bandIron rod