OEThe trick to this problem is recognizing that there is more than one possible arrangement for the points on the number line. Because BC is longer than AB, A could be either in between B and C or on one side of B with C on the other side of B,
Using the information about the midpoints (D and E) and the lengths of the line segments, you can fill in all the information for the two number lines:
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You can see that AE has two possible lengths: 1 and 9, however 1 is the only option that is an answer choice.