Final answer:
Option B, the sugar solution in a bird feeder with 25% sugar, has the highest concentration of sugar when compared to the other options provided.
Step-by-step explanation:
To determine which solution has the highest concentration of sugar, we need to compare the percentage of sugar by mass or volume in each solution. Option A provides insufficient information, as we do not know the total volume or mass of the solution; it only states 2 grams of sugar. Option B indicates the solution is 25% sugar, meaning if you have 100 grams or 100 milliliters of this solution, 25 grams or milliliters of that would be sugar. Option D states that nectar is 15% sugar, implying 15 grams or milliliters of sugar in 100 grams or milliliters of solution. As such, Option B, the sugar solution in a bird feeder with 25% sugar, has the highest sugar concentration.