Answer:
A. Tend to move in opposite directions (as one increases the other decreases)
Step-by-step explanation:
Voluntary cost is the cost that classified as a prevention & appraisal cost on the other hand the failure cost is the cost that could be internal or external.
The cost i.e. incurred for prevention so there would be less chances so if there is increase in the voluntary cost so there would be reduction in the failure cost and so on
Hence, the option a is correct