What is filed by sticker or decal number according to the inspection procedures?

Answer: B — The pink copy of the approval certificate

The pink copy of the approval certificate is filed by sticker or decal number according to the inspection procedures. This process is essential for tracking and record-keeping purposes, allowing authorities to reference specific inspections based on the unique identifier associated with each vehicle's sticker or decal. The filing system helps maintain a clear record of inspections, ensuring accountability and facilitating follow-ups if necessary. This also supports the overall goal of vehicle compliance with safety and emissions standards in Missouri. The other documents, while important, do not relate specifically to the filing process by sticker or decal number.