Answer
A) AB
B) $m\angle CBA$
Work Step by Step
A) We are told that we want the measure of the line segment. Since it asks for the measurement, we should use the letters with no symbols (like lines or rays) over the letters. Thus, the correct answer is AB.
B) We know that the two end letters of the angle can be changed, but the center point of the angle (the origination of the rays) always must be the middle letter. Since the middle letter is B, we know that the only allowable answer is $\angle CBA$.
