Hey there! I'm happy to help!
Isosceles triangles have at least two sides of the same length. We see that A and D are isosceles. It kind of looks like B does but if you look closely you will see that the there are not two matching sides.
Acute triangles have at least one angle that is less than 90 degrees. Triangles A and B are acute.
Right triangles have 1 right angle. Triangles C and D are right triangles.
Scalene triangles have sides of all different lengths. We see that B, C, and E are all scalene.
Therefore, the correct answer is There are exactly three scalene triangles.
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