The one is the same everywhere so we ignore it.

Choice B
For this case we have that by definition, a linear function is of the form

We have the following options:
A) 
Rewriting:

It's a quadratic function!
B) 
Rewriting:

It's a linear function!
C)
Rewriting:

It's a cubic function.
D) 
Rewriting:

It's a quadratic function!
E)
Rewriting:

It's a cubic function!
Answer:
The linear function is option B
Foil the equation; j*k, j*-5, 7*k, 7*-5, once you foil add like terms.
jk - 5j +7k - 35 is the final answer