Question

1. choose the best answer. tell what is wrong about the statement ∠abc equals 90°. diagram: point a above b, right angle symbol at b, point c to the right of b options: angle abc is obtuse. it should be the measure of ∠abc equals 90°. angle abc is acute. it should be ∠acb equals 90°.

Explanation:

• Analyze each option:
• Option 1: ∠ABC has a right angle symbol, so it's not obtuse (obtuse > 90°), so this is wrong.
• Option 2: When stating an angle's measure, we should say "the measure of ∠ABC" because ∠ABC is the angle itself, and we measure its size. The original statement incorrectly refers to the angle as equal to 90°; it should refer to the measure of the angle.
• Option 3: ∠ABC has a right angle symbol, so it's not acute (acute < 90°), so this is wrong.
• Option 4: ∠ACB is at point C, and from the diagram, the right angle is at B, so this is wrong.

Answer:

It should be "The measure of $\angle ABC$ equals $90^\circ$."