What must be marked on the MV-431 during a replacement process?

During the replacement process of a vehicle's inspection sticker, it is essential to mark "Replacement Sticker Issued" on the MV-431 form. This notation indicates that a new sticker has been provided to replace an older or lost one, which is critical for keeping accurate records of vehicle inspections and ensuring compliance with state regulations. Marking the form appropriately helps maintain the integrity of inspection records and allows law enforcement and inspection personnel to verify the current status of the vehicle's inspection without confusion.

The other options, such as "Issued," "Canceled," and "Obsolete," do not provide the necessary context specific to the replacement of an inspection sticker and could lead to misunderstandings about the vehicle's inspection status. Thus, "Replacement Sticker Issued" is the precise and required documentation for this specific situation.