If its got 2600 square feet, and 1 gallon covers 250 sq.ft., then you want the least number of gallons that must be purchased, and you can do it only with whole gallons. Well you divide the 250 into 2600; that gives you 10.4. Well, remember that you have to have a whole gallon; therefore, it can't be 10 because 10 won't cover it enough, but 11 would; so the answer is C, 11.