Write a rule for the linear function in the table

The answer is D. To figure this out, all you need to do is plug in the x's. 

A isn't correct because f(1) = 4(1), however, the chart says it equals 3.

B isn't correct because f(1) = 1 - 4, however, the chart says it should be 3 (not negative 3)

C isn't correct because f(1) = 1 + 4, but the graph says it's supposed to be 3, not 5.

That leaves D, but it's always great to double check. f(1) = 4 - 1. 3=3. Therefore, D is correct.