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Answer:
D. 90°
Step-by-step explanation:
The total number of degrees of arc in a circle is 360°. A diameter cuts the circle in half, and each half will be an arc of measure 180°.
An inscribed angle has half the measure of the arc it subtends. Angle B subtends an arc of 180°, so its measure is 180°/2 = 90°.
The measure of angle ABC is 90°.
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From this, you can tell that any triangle that is inscribed in a semicircle will be a right triangle. The angle opposite the diameter will have a measure of 90°.
