Final answer:
The direct cost of a training program is (d) Trainer preparation time.
Step-by-step explanation:
The direct cost of a training program refers to the expenses that are directly related to the program itself. Out of the options provided, the direct cost of a training program would be (d) Trainer preparation time.
Trainer preparation time is a direct cost because it involves the time and effort spent by the trainer in preparing the training materials, developing the curriculum, and organizing the content for the program.