The correct option is D Functional group
The points to be considered while writing the IUPAC names are:
-The number of carbon atoms in the parent chain, which is the longest continuous chain in a compound. This would give the root word of the compound.
- Presence or absence of unsaturation in carbon chain, determines the primary suffix of the compound i.e. whether the compound is alkane, alkene or alkyne.
- The functional group present as it can be an alcohol, an aldehyde, a ketone, etc. According to the functional group present, the secondary suffix in the name of the compound changes.
- Heteroatoms are those atoms, other than carbon and hydrogen atoms, which are attached to one or more carbon atoms in an organic compound. However, the valency of these atoms are not considered while naming an organic compound.