A proportional relationship means that the ratio of ingredients remains the same. Therefore, the sets of ingredients that are in a proportional relationship with the recipe are:
6 Tbsp oil, 1.5 Tbsp vinegar, 1 Tbsp honey (the ratio of oil:vinegar:honey is 2:0.5:0.33)
15 Tbsp oil, 4 Tbsp vinegar, 3 Tbsp honey (the ratio of oil:vinegar:honey is 12:3:2)
24 Tbsp oil, 6 Tbsp vinegar, 4 Tbsp honey (the ratio of oil:vinegar:honey is 12:3:2)
The other options are not in a proportional relationship with the recipe, as the ratio of ingredients does not remain the same.