Geometry

Question Analysis:
This question focuses on classifying triangles based on their angle measures.
The main focus is recognizing a right triangle, which has one 90° angle.

Key Concept Explanation:
Acute Triangle: All angles are less than 90°.
Right Triangle: One angle is exactly 90°.
Obtuse Triangle: One angle is greater than 90°.
Equilateral Triangle: All angles are 60°.

Step-by-Step Solution:
The given angles are 40°, 50°, and 90°.
One angle is 90°, which means the triangle is a right triangle.
Checking the answer choices:
(A) Acute Triangle: Incorrect, because one angle is exactly 90° (not all < 90°).
(B) Right Triangle: Correct, because one angle is 90°.
(C) Obtuse Triangle: Incorrect, as no angle is greater than 90°.
(D) Equilateral Triangle: Incorrect, because equilateral tr...