Each of the built－in costs of a product must bring in some profit at each stage: truckers

Each of the built-in costs of a product must bring in some profit at each stage: truckers must profit from transporting products, or they______ in business.

A．would not be

B．will not be

C．were not

D．can not be

请帮忙给出正确答案和分析，谢谢！