Choose the option below that is a characteristic of ketones.

a. They contain a carbonyl group that exhibits sp hybridization around the carbon atom.
b. They contain a carbonyl group with a nonpolar carbon-oxygen bond.
c. The functional group of this type of compound must always be on the end of a carbon chain.
d. The functional group of this type of compound must always be in the middle of a carbon chain.

Option d.

Explanation:

Ketones contain a carbonyl groups as a functional group, which is a carbon bonded to oxygen with a double bond. In a ketone, the carbon is always bonded to two carbon atoms:

R-C(=O)-R'  

The carbon in the carbonyl group has a hybridization sp2 (3 hybrid orbitals with an unhybridized p orbital), where two of the orbitals form sigma (σ) bonds with the other two carbons (R-C-R') and the other hybrid orbital form a sigma bond with the oxygen (C-O). The unhybridized p orbital on the carbon atom is used to form a pi (π) bond with the oxygen, thus forming the double bond (C=O).  

The bond of a carbonyl group is polar, because of the difference of the electronegativity between the carbon atom and the oxygen atom.  

Hence, from all of the above we can discard the option a, (the carbonyl groups exhibits sp2 hybridization), the option b (carbon-oxygen bond is a bond polar) and the option c (the group must always be in the middle of a carbon chain, the groups that are always in the end, are a aldehyde groups).

Therefore, the correct option is d, the functional group of this type of compound must always be in the middle of a carbon chain.

I hope it helps you!

d. The functional group of this type of compound must always be in the middle of a carbon chain.

Explanation: