Concept:The characteristic odour in billy goats is caused by male sex hormones, so removing the hormone source reduces or eliminates the smell.
Explanation:The strong odour in billy goats is mainly produced by hormones such as testosterone, which are secreted by the testes.
Castration involves removing the testes from the animal.
After castration, the production of these male hormones stops, and the characteristic odour is greatly reduced or removed completely.
Docking means cutting off the tail and has no effect on the odour.
Drenching means giving liquid medicine by mouth, while dipping means treating the animal for external parasites.
These methods do not target the source of the hormones responsible for the odour.
Answer:B. castrating