The difference in the weight of the grapes in the two bags is C) 275 oz.
In this problem we are given the information that one bag contains 750 ounces of grapes and the other contains 1,025 ounces. To find the difference in the weight, we must subtract:
1,025 - 750 = 275 oz.
Therefore, the difference in the weight of the grapes in the two bags is 275 oz., best represented by option C.