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: Pathology
True regarding unconjugated bilirubin is - 
Select and explain. 
A. Not lipid soluble, B. More water soluble, C. Excreted by kidney easily, D. Bound with serum albumin
D: Bound with serum albumin
Answer: D: Bound with serum albumin 
Explanation: Unconjugated bilirubin 

Unconjugated bilirubin is highly lipid soluble (lipophilic).
It is insoluble in water and tightly bound to albumin → cannot be excreted in urine.
Unbound fraction, which is increased in hemolytic reactions (e.g. erythroblastosis fetalis), can cross blood-brain barrier because of lipophilic nature and can cause brain damage of newborn → Kernicterus.

Conjugated bilirubin

Conjugated bilirubin is water soluble and only loosely bound to albumin and thus is easily filtered by glomeruli and excreted in urine.