Answer: A parallelogram, since both pairs of opposite sides are equal and the diagonals bisect each other.
- A A parallelogram, since both pairs of opposite sides are equal and the diagonals bisect each other
- B An equilateral triangle with one repeated vertex according to standard results
- C A regular tetrahedron in most documented configurations
- D Four collinear points under typical conditions
Correct answer: A. A parallelogram, since both pairs of opposite sides are equal and the diagonals bisect each other
Explanation: The midpoints of AC and BD coincide, which is the defining test for a parallelogram: the diagonals bisect each other.
Concept context
Coordinate axes and planes in space, octants, distance between two points, and the section formula
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