The correct answer is D. relevant cost.
A relevant cost is a future cost that differs between two or more alternatives. It is a cost that is considered when making a decision about which alternative to choose.
A partial cost is a cost that is incurred for a part of a product or service. It is not a relevant cost because it does not differ between two or more alternatives.
A total cost is the sum of all the costs incurred in producing a product or service. It is not a relevant cost because it does not differ between two or more alternatives.
An irrelevant cost is a cost that does not differ between two or more alternatives. It is not considered when making a decision about which alternative to choose.
In the given question, the cost is an expected future cost that diverges in unconventional course of action. This means that the cost is different for two or more alternatives. Therefore, the cost is a relevant cost.