For some integer every odd integer is of the form :
Let, an integer is represented as
When is an odd integer,
Suppose then are correct because is already odd and is also odd.
When is an even integer,
Suppose then (b), (d) are correct because,
Therefore. It is clear from both cases is the only option that is every odd integer is of the form since options are incorrect.
Hence, the correct answer is option (d),