This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other topics and Adverse effects, Subject name: Pharmacology
Which of the following drugs is LEAST effective luminal amoebicide? 
Select and explain. 
A. Metronidazole, B. Diloxanide furoate, C. Iodoquinol, D. Paromomycin
A: Metronidazole
Answer: A: Metronidazole 
Explanation: (Ref: KDT 6/e p798, 799) Metronidazole is least effective luminal amoebicide because it is almost completely absorbed in small intestine and little drug is available to act in the colon.