Quadrilateral Classification: Analyzing ABCD with Perpendicular Diagonals

The problem requires determining if a given quadrilateral is a deltoid, and if so, whether it is convex, concave, or indeterminate based on the provided diagram. A deltoid, or kite, is generally defined as a quadrilateral with two pairs of adjacent sides being of equal length. Thus, a visual analysis is essential here as only diagrammatic data is available.

To address this, one must closely analyze the properties of the given quadrilateral in terms of similarity and its symmetry relative to a conventional deltoid structure:

• Typically, you'd look for simultaneous symmetry or patterns indicating two equal-length adjacent pairs of sides.
• After examining the diagram and the naming convention (vertices labelled A, B, C, D), see if it implies any such congruency visually or through label symmetry.
• Lack of distinct clues for equal side pairs or diagonals prevents concluding its specific nature without additional information, especially since no specific length measures or angles are provided.

Given this and under diagram-only conditions, it's not possible to definitively prove that the shape is completely a deltoid (convex or concave). Therefore, without further data, identifying the indicated quadrilateral deltoid nature is beyond determining from the given data itself.

Consequently, the correct answer is: It is not possible to prove if it is a deltoid or not.