The first step is to find out the longest carbon chain starting from the carbonyl group. In other words, the numbering starts from the carbonyl group to the last carbon of the longest chain.

The suffix “al” is used for aldehyde, whereas “one” is used for ketone.

a. The given compound is composed of a five-carbon chain. The CHO group and two methyl groups are attached to C-1 and C-4 atoms, respectively.

The IUPAC name of the given compound is shown below:

4,4-dimethylpentanal

b. The given compound has eight carbon atoms in a chain. The -CHO group and methyl groups are attached to C-1 and C-5, C-6 atoms, respectively.

The IUPAC name of the given compound is shown below:

2,5,6-trimethyloctanal

c. The given compound has four carbon atoms in a cyclic form. The CHO group and two chlorine atoms are attached to C-1 and C-3 atoms, respectively.

The IUPAC name of the given compound is shown below:

3,3-dichlorocyclobutanecarbaldehyde