This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Bilirubin secretion is stimulated by 
Select and explain. 
A. Bile salts, B. Bile pigments, C. Secretin, D. CCK
A: Bile salts
Answer: A: Bile salts 
Explanation: Bile salts are the most important cholerectic or the substance that increases bile secretion. Cholecystokinin (CCK) is the most important cholagogue or substance that increases gallbladder contraction.