In the `IUPAC` name of the following compound, there something wrong. Find the mistake.
`N-`ethyl `-6-`oxo`-5-`propyl heptanamide
A. Principal functional group is incorrectly chosen
B. Incorrect prefix for locant is used
C. Parent chain is incorrectly selected
D. Locants name is not written in order of priority recommended by `IUPAC`.