See below. The graph is in a straight line, also known as linear. The other graphs are not. Also, if you look at the range (y) of the tables, you can see the increase is linear as it is increasing by .5 (1/2) everytime.
Yes I agree with that because you combined the terms in the monomial correctly and the degree of the monomial was greater then the degree of any other mono/binomials in the polynomial