Concept:Angles are classified by measure: acute (<90°), right (90°), obtuse (90° to 180°), straight (180°), and reflex (180° to 360°).
Explanation:Check each statement one by one.
Option A: An acute angle plus 90° always gives an angle between 90° and 180°, which is obtuse. This is true.
Option B: Two acute angles (each <90°) could sum to more than 90°. For example, 50°+50°=100° > 90°. So this statement is false.
Option C: Two right angles (90°+90°=180°) form a straight angle. This is true.
Option D: Each obtuse angle is >90°, so their sum is >180°, which is a reflex angle. This is true.
Only option B is false.
Answer:The statement that is not true is option B.