Concept:Tapeworm, liver fluke, and roundworm are internal parasites, so control involves oral medication.
Explanation:These worms live inside the animal's digestive system or organs.
Drenching means giving liquid medicine by mouth to kill internal worms.
Anthelmintic drugs are used for this purpose.
Dipping treats external parasites like ticks and lice.
Flushing and fumigation do not target internal worms.
Therefore, drenching is the correct method of control.
Answer:B. drenching