The correct option is
D ![](https://lh6.googleusercontent.com/eTtxUZnHeAoHV1LsywTdl9BoCstZQ5Xg-PK4eI_OhNTAn3_DIUGZyEX5yoSZXcYdwKHjArgRb3m-HZs7rxR8xPD0vl97837v1VDqJhrYBQ7cnA3iLjqmSkZSa4UmgHNKAE2FWJVD)
We know the representation of a linear function on the graph is a straight line.
Option A:
The given graph is a straight line.
And as the graphical representation of any linear function is a straight line, so it is a linear function.
Option B:
The given graph is a straight line.
And as the graphical representation of any linear function is a straight line, so it is a linear function.
Option C:
The given graph is in the combination of multiple lines. It is not a single straight line.
And as the graphical representation of any linear function is a straight line, so it is a nonlinear function.
Option D:
The given graph is a straight line.
And as the graphical representation of any linear function is a straight line, so it is a linear function.
So option C is the correct answer.