To classify the triangle based on its angle measures:
- Acute Triangle: All angles are less than 90°.
- Right Triangle: One angle is exactly 90°.
- Obtuse Triangle: One angle is greater than 90°.
In the given triangle, the angles are 46°, 51°, and 83°. All of these angles are less than 90°.
Since all angles are less than 90°, this triangle is classified as an acute triangle.
So, the correct answer is acute triangle.