Final answer:
When a line segment is translated on a coordinate plane, its length and orientation remain the same. Line segment AB has a length of 2 units and is translated 6 units to the right to obtain line segment A'B', which also has a length of 2 units.
Step-by-step explanation:
When a line segment is translated on a coordinate plane, it means that it is moved horizontally or vertically without changing its length or orientation. In this case, line segment AB is translated 6 units to the right. Since the length of AB is 2 units, the length of A'B' will also be 2 units. Therefore, the correct answer is (a) 2 units.