A professional seal indicates that a licensed professional has taken responsibility for the document and applied professional judgment in its preparation, review, and approval for its intended use. In Ontario, a drawing bearing a valid professional seal implies it was prepared by or under the responsibility of a person authorized to practise in Ontario (i.e., an Ontario licence holder or appropriately authorized practice entity), so A is the best statement. Sealing does not mean the regulator has reviewed or approved the document (C is false); regulators generally do not pre-approve individual drawings. A sealed drawing is also not automatically transferable across all jurisdictions without regard to local licensing and code requirements (B is false), and it is not necessarily reusable on any site even within Ontario (D is false) because designs are site- and project-specific and rely on assumptions (loads, soil, climate, codes, and constraints) that may not hold elsewhere. Therefore, A is correct.