An acute triangle is one in which all its angles measure less than 90 °.
The triangle of the figure has the angles: 51 °, 51 °, 78 °
Which are all less than 90 °, thus it is an acute triangle.
We discard options A.Obtuse and B.Right because an obtuse triangle has an angle of more than 90 °, and a right triangle has an angle of exactly 90 °, and none of these definitions match the triangle in the image.
