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: Biochemistry
The important intermediate product of biosynthesis of fatty acid is 
Select and explain. 
A. Cholesterol, B. Malonyl CoA, C. Acetyl CoA, D. Thioesterases
B: Malonyl CoA
Answer: B: Malonyl CoA 
Explanation: Malonyl CoA 

Acetyl-CoA is the immediate substrate for fatty acid synthesis.
However, acetyl-CoA needs to be converted to the activated form, which will serve as the donor of carbon units to the growing fatty acid chain.
Malonyl-CoA is such activated form; acetyl-CoA is converted to malonyl-CoA by acetyl-CoA carboxylase.