A proportional relationship is a relationship in which the ratios of two variables are equivalent.
If we take two points on the graph such as (45, 30) and (30, 20), we can see that they can both be simplified to the ratio 3:2. Using this we can find the correct answer. From looking at all the points we can see that only (90,60) would also form a ratio of 3:2, thus d would be the correct answer.
