The correct answer is A. An Inflow.
Savings in respect of a cost is treated in capital budgeting as an inflow because it represents a reduction in future costs. This reduction in costs will lead to an increase in future cash flows, which is a positive factor in capital budgeting.
Option B is incorrect because savings are not an outflow. Outflows are costs that are incurred in the present in order to generate future benefits. Savings, on the other hand, are reductions in future costs.
Option C is incorrect because savings are not zero. Savings represent a reduction in future costs, which means that they are a positive amount.
Option D is incorrect because savings are not none of the above. Savings are a real and measurable amount that can be used in capital budgeting.