The correct answer is: C. Less than X.
The output of a drag-line is affected by the angle of swing and the depth of cut. The greater the angle of swing, the less material the drag-line can excavate in a given amount of time. The greater the depth of cut, the more material the drag-line can excavate in a given amount of time.
If the output of a drag-line for 90° angle of swing at optimum depth of cut is X, then the output for 120° angle of swing at 120% of optimum depth of cut will be less than X. This is because the greater angle of swing will reduce the amount of material that the drag-line can excavate in a given amount of time, and the greater depth of cut will not compensate for this reduction.
Option A is incorrect because the output of the drag-line will not be equal to X. Option B is incorrect because the output of the drag-line will not be more than X. Option D is incorrect because the output of the drag-line will not be any of the above.