<h3>Answer:</h3><h3>There are 3 true statements, and the true statements are: </h3><h3>choice A, choice C, choice D</h3>
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Explanation:
A. True. All triangles have 3 straight sides and 3 angles.
B. False. All triangles are polygons. A polygon is just a collection of line segments glued together to form a closed shape.
C. True. A plane figure is a flat shape.
D. True. See choice A.
E. False. Some triangles do not have one right angle. Example: obtuse triangles do not have any right angles.
