Which type of isomerism is shown by pentanone? A) Chain B) Position C) Functional

•  Pentanone is an example of chain, position and functional isomerism. 
• Chain isomerism is when the same molecular formula is represented by different arrangements of atoms in a chain. 
• Position isomerism is when the same molecular formula is represented by different positions of functional groups in the same chain. 
• Functional isomerism is when the same molecular formula is represented by different functional groups in the same chain.

Therefore, the correct option is D. A, B and C.