Daphne makes 5 bows for every 3 feet of ribbon, this means that for every 3 feet increase in length of ribbon the bows increases by five. So,
For 3 feet, bows are 5,
For 6 feet bows are 10,
For 9 feet bows are 15,
For 12 feet bows are 20
For 15 feet bows are 25,
for 18 feet bows are 30,
For 21 feet bows are 35,
For 24 feet bows are 40.
For 27 feet bows are 45
For 30 feet bows are 50.
Thus option C is correct.