Step 1: Identify the grammatical construction used.
The sentence uses the correlative conjunction “not only … but also”.
Step 2: Check whether the construction is complete.
In the given sentence, the word “also” is missing after “but”.
Correct form should be:
\[
\text{The officer is not only greedy but also corrupt.}
\]
Step 3: Locate the part containing the error.
The error lies in part (C) because it should read “greedy but also corrupt”.
Step 4: Final conclusion.
Hence, the incorrect part of the sentence is (C).