PAN-SH site of fatty acid synthase complex accepts: (A) Acetyl CoA, (B) Malonyl CoA, (C) Propionyl CoA, (D) All
Answer is B. Malonyl - CoA 

Central thiol or Pan -SH or 4-phosphopantetheine of ACP →  Accepts malonyl group
Peripheral thiol or cysteine -SH group of 3-ketoacyl synthase  → Accepts acetyl group