Answer: Choice B

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Step-by-step explanation:
The measure of any minor arc is always less than 180 degrees. So it will have a smaller measure than a semicircle. Arc ADB is over 180 degrees, so we can rule that out. Minor arc AB is the measure from A to B following the shorter path along the circle, which would be 115 degrees (the longer path would be 360-115 = 245 degrees)
In other words, the central angle ACB is equal in measure to minor arc AB. Both describe the same basic idea when it comes to circles and their angle measures.