When a line is rotated, it is rotated about a fixed point to its new position. Line AB must turn 180 degrees about point A to coincide with line AE.
The complete question is that we determine the angle which AB will turn to, about point A to align with AE (see attachment for the figure)
Line AB and AE form a straight line. This means that the angle between these two lines on either side of point A is [tex]180^o[/tex]
So for line AB to coincides with line AE, the line AB must turn 180 degrees about point A.
Hence, option (B) is correct.
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