Ageometry teacher asked charlene to define “acute triangle.” charlene said that an acute triangle is a triangle whose three interior angles have measures less than 90°90°. is charlene’s definition valid? a. yes, because no right triangles fit this definition. b. no, because some scalene triangles fit this definition. c. yes, because this definition fits all acute triangles and does not fit triangles that are not acute. d. no, because not all acute triangles fit this definition.